Sciencemadness Discussion Board - The short questions thread (2)

The short questions thread (2)

Pages: 1 2 3 4 5 6 .. 8

turd - 9-8-2009 at 12:44

Does anybody know a synthesis for 3-methoxy-4-halobenzaldehyde from reasonably common materials? I thought it would be a simple case of bromination of Vanillin. I was mistaken.

Formula409.

A quick Scifinder search reveals that it mostly turns around oxidation of the corresponding benzyl alcohol (or even toluene compound) or the reduction of the benzoic acid. Nothing really home chemistry friendly.

Journal of Medicinal Chemistry, 35, 4408-14 (1992)
Tetrahedron Letters, 46, 5417-5419 (2005)
International Patent Application 2007044804
Journal of Medicinal Chemistry, 30, 1887-91(1987)

bfesser - 10-8-2009 at 11:05

I'm setting up an apparatus to generate and bubble HCl through water. Should I use natural latex or silicone tubing to connect the gas generator to the bubbler?

ammonium isocyanate - 10-8-2009 at 20:51

Will methylating agents such as iodomethane, methyl nitrate, or DMS add across alkene bonds in fatty acids?

Picric-A - 12-8-2009 at 12:38

no, to add to alkenes fatty acid you must use the cyanide route.

kclo4 - 12-8-2009 at 13:20

Quote: Originally posted by bfesser

I'm setting up an apparatus to generate and bubble HCl through water. Should I use natural latex or silicone tubing to connect the gas generator to the bubbler?

I doubt the HCl/Hydrochloric acid would do much damage in the time the tube is exposed to it. Personaly, I think I'd use silicone, I'd bet it would probably hold up better then a natural latex, but I don't have any thing that could confirm this.

Make sure you take the steps to prevent suck back, as that could have very bad results.

JohnWW - 12-8-2009 at 13:48

The addition of prussic/cyanic/hydrocyanic acid, HCN to the double bond of alkenes to form a nitrile, as Picric-A implies, thereby adding an extra C atom, appears to be a fairly recently-discovered and little-known reaction, requiring the use of Ni or (more expensively) Pd as a catalyst, involving the formation of a metallic complex. It does not seem to be in the organic textbooks I have. I had difficulty finding it on Google, but I finally found it using the search phrase "hydrocyanation of alkenes". It is analogous to the addition of an halo-acid across the double bond of an alkene, as per the Markownikoff rule; but it would, uncatalyzed, be VERY MUCH slower, because of the weakness of HCN as an acid. It is also analogous to the cyanohydrin reaction of aldehydes and ketones with HCN, which is the best-known method of adding an extra C atom.

Restricted literature references I found for it are; someone with access please download and post these articles in References:
http://www.springerlink.com/index/w785m3234h21j50w.pdf
(this is chapter 11 of a very recent book)
http://doi.wiley.com/10.1002/9783527619450.ch4
http://pubs.acs.org/doi/abs/10.1021/om00098a011
http://pubs.acs.org/doi/abs/10.1021/ol062002f
http://doi.wiley.com/10.1002/9783527619405.ch2f

I found only these worthwhile unrestricted references to it, out of 556 results:
http://alexandria.tue.nl/extra2/200612186.pdf
http://www.patentstorm.us/patents/5175335/description.html
http://www.ncbi.nlm.nih.gov/pubmed/19072815
http://sciencestage.com/d/51307/self-assembled-bidentate-lig...
http://d.wanfangdata.com.cn/NSTLQK_NSTL_QK18502590.aspx
http://www.lavoisier.fr/notice/fr427287.html
http://www.labmeeting.com/paper/28609235/de-greef-breit-2009...
http://www.researchandmarkets.com/reports/693304/catalysis_i...

Other addition reactions that alkenes undergo under ordinary conditions, not counting oxidative cleavage (with KMnO4, OsO4, O3, etc.), resulting in a single C-C bond, are: (a) addition of halogens in the dark across the double bond to form vic-dihalides (the presence of UV light would cause H atoms elsewhere in the molecule to also be replaced); (b) addition of haloacids (HI etc) across the double bond to form a monohalide, the position of the H and of the halide being according to the Markownikov rule; (c) catalytic (with Ni or Pd) hydrogenation, in which H2 is added to the bond, making it an alkane; (d) acid-catalyzed addition of water to make an alcohol; and (e) reaction with a peroxy-acid to form an epoxide.

[Edited on 12-8-09 by JohnWW]

Attachment: HydrocyanationOfAlkenes-FirstPage(springerlink_com).pdf (126kB)
This file has been downloaded 1349 times

crazyboy - 13-8-2009 at 12:54

Is it ok to use a flat bottom flask as a receiving flask in vacuum distillation? I know RB is preferable but the joint size is uncommon...

DJF90 - 13-8-2009 at 13:24

No, not if you want it to remain in one piece.

497 - 13-8-2009 at 13:27

Hmm I thought I've read that as long as the FB flask is of reasonable thickness it would survive fine. And in fact I have pulled a vacuum in FB flasks a few times and never had problems. Can someone confirm this?

DJF90 - 13-8-2009 at 13:51

If you want to be safe, then I wouldnt even consider using a FB flask. Of course a "reasonable" thickness will be fine - thats why buchner flasks have to be made with thicker than normal walls. I doubt you'll find a FB flask like that unless its been specially made. And of course it also depends on the strength of the vacuum being pulled. But in short - not something I would do.

jones oxidation

raynoid - 17-8-2009 at 03:16

Hi, long time viewer first time poster..

Have always had a great interest in chemistry and am currently studying it at university and have fun with it at home too.

I have UTFSE but I couldnt find an answer on preparing a Jones reagent solution as I'm currently doing some experimenting with it. I am aware of its preparation with CrO3 but would prefer to use K2Cr2O7 as it is easier for me to obtain, could someone help me with preparing a 1M solution of this?

woelen - 17-8-2009 at 08:59

I would say, use the preparation with CrO3, but replace the amount of CrO3 with half the amount of K2Cr2O7 (not weight-wise, but molar-wise) and add some extra acid to account for the "K2O" in the potassium dichromate. This results in Jones reagent with some extra K2SO4 in solution, which should not make any difference in the majority of reactions.

S.C. Wack - 17-8-2009 at 12:35

The solution (added to) is usually cold acetone...so that may not stir so well after a while.

Paddywhacker - 17-8-2009 at 23:07

You'll have to master molarities and simple problems like this to get anywhere in chemistry.

It looks, from my googeling, that Jones Reagent is 25% CrO3 in 25% H2SO4 in water. As the molecular weight is 100, that is 2.5 Molar. You want a more dilute solution, 1.0 Molar. Theoretically, you should be able to use an equivalant amount of K2Cr2O7, as the acid is in vast excess.

The molecular weight of K2Cr2O7 is about 294, and of course, each mole of that contains two moles of Cr, so halve that to give 147 g/litre in 25% H2SO4, or 14.7 % in 25% H2SO4 for a 1 molar Jones Reagent.

You've departed from the formula, which was to use CrO3, so your mileage may vary.

raynoid - 18-8-2009 at 00:12

Thanks for all the help so far, can anyone comment on the use of jones reagent in regards to oxidation of an aldehyde to a carboxylic acid. Such as how many moles will a solution of the reagent potentially oxidize as I cant seem to find a definitive answer and yes I did search, but their doesnt seem to be a great amount of literature on it unless I'm looking in the wrong places, if so a point in the right direction would be much appreciated!

Edit: Found this on the forum "As I seem to remember, the standard solution I used to use for permanganate was 0.05M. And it was still intensely coloured. Dichromate solution IIRC is made up to 2M in 2M sulfuric acid. (i.e. 2 moles of sulfuric acid and 2 moles of K2Cr2O7 in 1L of water)"

Does this sound about right?

[Edited on 18-8-2009 by raynoid]

DJF90 - 18-8-2009 at 08:53

You can work out the stoichiometry using the half equations for the reactions:

Cr2O7(2-) + 8H(+) + 6e(-) => Cr2O3 + 4H2O

and

RCH2OH => RCHO + 2H(+) + 2e(-)

Then you can multiply the second equation by 3 to balace the number of electrons with the first, and then add the two equations so the electons cancel out. Some of the hydrogen ions also cancel:

Cr2O7(2-) + 2H(+) +3RCH2OH => Cr2O3 + 4H2O + 3RCHO

So one mole of dichromate theoretically oxidises 3 moles of alcohol to the corresponding aldehyde (or ketone). The half equation for oxidation of aldehyde to carboxylic acid is:

RCHO + H2O => RCO2H + 2H(+) + 2e(-)

I'll let you work out the stoichiometry for this one yourself; I've done the hard part.

[Edited on 18-8-2009 by DJF90]

Klute - 1-9-2009 at 20:04

Is it possible to C-alkylate benzoquinone? I know addition of various nucleophiles (thiolates, alcolates, etc) give the addition product hydroquinone, would carbanions like methylmagnesium bromide act similarily? Or would it add on the carbonyl?

Basicly, is there a way of producing 2-alkylbenzoquinones or 2-alkylhydroquinones from benzoquinones and alkyl halides?

Google seraching revealed nothing..

DJF90 - 2-9-2009 at 07:15

I would expect this to be the case - organocopper reagents give 1,4-addition in preference to 1,2-addition; using a grignard reagent with a small small quantity of a copper (I) salt (IIRC). You might also try organocadmium reagents, if you dare.

not_important - 2-9-2009 at 07:15

I know naphthoquinone and some benzoquinones can be C-alkylated via a free radical process using the one carbon longer carboxylic acid and red lead Pb3O4. I'll try to find references tomorrow.

Slightly rekated, may be of interest:

Tetrahedron Letters
Volume 50, Issue 36, 9 September 2009, Pages 5116-5119
doi:10.1016/j.tetlet.2009.06.107

Klute - 2-9-2009 at 21:16

hum, doesn't look as simple as I thought.. Too bad..

Totally unrealted question: does anyone see why trimethylphosphate couldn't be used to form methyl esters? It could be used to form methyl tosylate from tosyl acid or a tosylate salt, as trimethyl orthoformate does (Link)..

In some case trimethylphosphate can't be used as methyl tosylate, ei the alkylation of aldimines: TMP gave no product after reflux overnight with the benzaldimine of 2-phenethylamine, while TsOMe reacted completly..

If I try this reaction, I'm not sure how I could check that the tosylate has been methylated.. I'm not sure TLC would work here, don't think TMP will show under UV.. And how to seperate the tosylate from excess TMP?

Might just better be off staying with the tosyl chloride + methanol method.. and keep the TMP for other things.. One thing I really want to try is alkylation of aliphatic amines with TMP.. Maybe N-monomethylation could result.. at least dimethylation with no quaternization, as for anilines (article)

solo - 4-9-2009 at 10:07

I'm trying to find the melting point of the amide of
MDA (N-Formyl MDA_).....thanks.....solo

[Edited on 4-9-2009 by solo]

solo - 5-9-2009 at 19:46

I'm trying to find the melting point of the amide of MDA and it's proper name as it's not N-formyl MDA..... and was not able to edit my previous post ......thanks.....solo

By chamula

Paddywhacker - 7-9-2009 at 00:36

Quote: Originally posted by not_important

I know naphthoquinone and some benzoquinones can be C-alkylated via a free radical process using the one carbon longer carboxylic acid and red lead Pb3O4. I'll try to find references tomorrow.
...

Yes please.

sparkgap - 7-9-2009 at 16:31

Quote: Originally posted by solo

the amide of MDA and it's proper name as it's not N-formyl MDA

If we're going with strict IUPAC: 3-(benzo[d][1,3]dioxol-5-yl)-2-methylpropanamide

If we use the "methylenedioxy" device: 2-methyl-3-(3,4-methylenedioxyphenyl)-propanamide

sparky (~_~)

sonogashira - 8-9-2009 at 11:31

There is a reference to "a-Methyl- 3,4-methylenedioxyphenylpropionamide" in this paper starting at the bottom right on page 2 which may be useful for physical properties data

Attachment: a -Methyl-3,4-methylenedioxyphenylpropionamide.pdf (435kB)
This file has been downloaded 617 times

[Edited on 8-9-2009 by sonogashira]

ketel-one - 8-9-2009 at 17:08

Short question, I know it's very beginnerish

When you cleave an ether R1-O-R2 with boiling HI, you get R1-OH and R2-I, right? If you got R1-OH and R2-OH it probably would just be called hydrolysis. And can you use HI3 instead of HI?

kclo4 - 8-9-2009 at 17:36

I assume HI3 is a mix of HI and I2, and is used to increase the solubility of I2 in solution?
I don't think it would be wise to use..

ketel-one - 8-9-2009 at 17:57

Alright I suppose I'd bubble some hydrogen through it to make more HI, I don't exactly have any H2S

And forget about the first question I've figured out already you do get R1-OH + R2-I
http://www.brainmass.com/homework-help/chemistry/organic-che...

not_important - 8-9-2009 at 20:36

Quote: Originally posted by ketel-one

Alright I suppose I'd bubble some hydrogen through it to make more HI, I don't exactly have any H2S

That will give you hydrogen gas containing a bit of elemental iodine, the reaction is very slow without a catalyst.

You can use iodine, water, and H2S, which give aqueous HI and elemental sulfur; iodine, water, and SO2, which gives you aqueous HI and H2SO4; or I2, H2O, and red phosphorous, the favorite of meth makers.

kclo4 - 8-9-2009 at 20:44

Sulfur is easy to get, and you can make H2S easily from it by heating it with wax.
SO2 can obviously be made by burning the sulfur.

ketel-one - 8-9-2009 at 20:55

Oh right I just remembered a good way to get sulfur... Lots of matches in HCl, i believe last time I tried it it also made Cl2O or something... I forget it was a couple years ago.

dann2 - 9-9-2009 at 02:29

Hello,

Quote: Originally posted by kclo4

Sulfur is easy to get, and you can make H2S easily from it by heating it with wax.

How do you do that. Simply heat Sulphur and candle wax together?
Dann2

woelen - 9-9-2009 at 04:12

Yes, simply heat a mix of sulphur and paraffin. Use excess paraffin. If you buy white candles, then try to find the paraffin ones. There also are stearin-based candles and these may react in a different way. Paraffin can also be purchased from eBay as a pure chemical, it just is an alkane with many C-atoms in a chain (IIRC numbers of C atoms is more than 20).

When the mix of sulphur and paraffin is heated, then the paraffin melts, the sulphur also melts, but somewhat later. On stronger heating the mix starts fuming and bubbling. The fume is due to evaporation and recondensation of paraffin, the bubbles you obtain consist of H2S gas. Purification can be achieved by bubbling through paraffin oil (which also is a mix of alkanes, but with somewhat lower number of C-atoms). The paraffin fumes dissolve in the paraffin oil, the H2S bubbles through the oil. Try to pass large bubbles of gas through a tall column, otherwise you will suffer from excessive foaming.

Be warned though, that this procedure is very messy. Your reaction vessel is covered by a gummy very hard to remove material which has a terrible smell. I once did the experiment in a large and wide test tube. I decided to discard that tube, it simply appeared impossible to make it clean again. Also keep in mind that H2S is very toxic, one of the members of this forum almost passed out after inhaling too much H2S. The sense of smell is deadened by high concentrations of H2S, this introduces an additional safety risk.

[Edited on 9-9-09 by woelen]

Klute - 9-9-2009 at 04:40

I really advise against using H2S, even in a sealed apparatus. The event of a leak is just too dangerous. I was thinking I could handle it with a good scrubber, but didn't realize that even after gas generation has finished the sludge still contains enough H2S to kill someone. I had a very bad and frightening experience with it. Certainly not something for newbees or even intermediates..

ketel-one - 9-9-2009 at 11:32

Quote: Originally posted by Klute

Certainly not something for newbees or even intermediates..

Right I guess that's my que.

entropy51 - 9-9-2009 at 12:29

And here you are crapping all over another thread.

They're just BS'ing you man. H2S isn't poisonous. Make all you want.

JohnWW - 9-9-2009 at 13:05

Quote: Originally posted by entropy51

(cut)They're just BS'ing you man. H2S isn't poisonous. Make all you want.

Oh yeah? Besides being smelly, the stuff is DEADLY poisonous, being comparable to HCN or (CN)2, HOCN, CO, CH2N2, PH3, and HN3, as gases or vapors, and their salts, which have a similar mode of action entailing preferential bonding to the Fe atom in hemoglobin in place of O2. There are some people here who apparently do not want to see you back, so you could oblige them by making and breathing in a large enough amount of the stuff.
P.S. If your statement was intended as a joke, there are, unfortunately, those naïve enough to take it literally.

[Edited on 9-9-09 by JohnWW]

entropy51 - 9-9-2009 at 14:10

Thank you, John for ruining my joke.

watson.fawkes - 9-9-2009 at 14:37

Quote: Originally posted by Klute

I really advise against using H2S, even in a sealed apparatus. The event of a leak is just too dangerous.

I'll second this, not from experience, because I don't intend to have any with this. Don't make H2S in a sealed apparatus made out of iron pipe, even. H2S causes sulfide embrittlement in iron and steel, causing cracking from the inside that leads to a sudden rupture visible from the outside. Industrially, when significant quantities of H2S are present, various high-nickel alloys are specified, such as the Hastelloy series, and those are pricey. This is even something to worry about with ordinary sulfur, as moisture + sulfur + heat makes non-trivial amounts of H2S.

Formula409 - 9-9-2009 at 22:19

Can brominated bicyclic molecules be used as alkylating agents? For example, 2-bromo-1,7,7-trimethylbicyclo[2.2.1]heptane (i.e. borneol [alcohol of camphor] brominated at the OH):

Many thanks!

Formula409.

[Edited on 10-9-2009 by Formula409]

[Edited on 10-9-2009 by Formula409]

Formatik - 10-9-2009 at 01:17

What liquid substance will dissolve the most substances at room temperature? Water? DMSO?

Paddywhacker - 10-9-2009 at 03:38

Quote: Originally posted by Formula409

Can brominated bicyclic molecules be used as alkylating agents? For example, 2-bromo-1,7,7-trimethylbicyclo[2.2.1]heptane (i.e. borneol [alcohol of camphor] brominated at the OH):

Many thanks!

Formula409.

In what way ... Friedel-Crafts? I doubt it.
But it should react with a Grignard, and should form a Grignard, and alkylate that way.

This compound can be made, I think, from alpha pinene and dry HBr. Any reason why it wouldn't react as I suggest?

DJF90 - 10-9-2009 at 03:56

I suspect making the grignard reagent will work oks. Also the alkyllithium, possibly by lithium-bromine exchange with MeLi or the likes. You havent staed as to whether the bromine substituent is endo or exo, and suspect that only the endo-isomer (I hope I've got this right) will react in any form of Sn2 (albeint probably poorly) with nucleophilic reagents as there is too much steric hindrance for the approach of the nucleophile in the exo isomer (and this may be the case with the endo isomer too...)

JohnWW - 10-9-2009 at 06:35

Yes, a secondary bromide like that one could be made into a Grignard reagent, for introduction of a 2-bromo-1,7,7-trimethylbicyclo[2.2.1]heptanyl group into another alkyl or aryl halide, substituting for the halogen. In addition, that secondary bromide would show some dissociation into a carbocation in a polar aprotic solvent, enabling it to be used for electrophilic addition reactions, e.g. to amines to make substituted amine salts, or to alcohols or ketones or aldehydes to make ethers, or possibly under some conditions to ethers to make oxonium salts.

Nicodem - 10-9-2009 at 08:32

I don't know exactly which compound Formula409 is asking about (the structure is ambiguous) since the bromination of borneol can give two compounds, bornyl bromide or isobornyl bromide, or a mixture of two, depending on the method used. The examples in the literature use some pretty hard to obtain reagents. Therefore, I have no idea how Formula409 intents to obtain (iso)bornyl bromide except maybe from HBr addition on pinene like Paddywhacker suggested (described in Journal of Organic Chemistry, 51, 4947-4953).
In any case an SN2 substitution is nearly impossible on the two bornyl bromides, because it is a stericaly hindered, bridged, cyclic and secondary bromide (each of these factors is deactivating for SN2 mechanism). It might be possible with S-nucleophiles or other extremely strong and not too basic nucleophiles. Under basic conditions only an E2 mechanism can result. An SN1 would most likely give a rearrangement product(s) and in any case is only possible in an acidic media so the choice of nucleophiles (which Formula409 failed to specify) is very limited. There are examples of some SET based nucleophilic substitutions on such systems described in the literature (for example the mechanistical study in Tetrahedron Letters, 30, 493-496), but I doubt this is relevant.

JohnWW, aliphatic secondary alkyl bromides do not dissociate to carbocations just like that, certainly not in absence of any acid! There is no way you can get an SN1 substitution with amines on normal secondary alkyl halides and I wish you could provide a reference if you know about any such example. Only tertiary alkyl halides and some alkyls stabilized by resonance can participate in SN1 reactions in neutral or basic media. You would need the presence of a very strong acid, AlBr3 for example, to get something resembling a carbocation, but only transiently resembling. And obviously this is not possible in the presence of such nucleophiles like the amines because they are too basic. I could find no examples for your suggestion of using (iso)bornyl bromide derived Grignards in a Kumada coupling, but there are some examples of Kumada, Suzuki and Stille couplings using Grignard reagents on norbornyl bromides (that is similar, but in the reversed role of reaction partners, from what you proposed).

JohnWW - 10-9-2009 at 18:57

Quote: Originally posted by Nicodem

(cut)JohnWW, aliphatic secondary alkyl bromides do not dissociate to carbocations just like that, certainly not in absence of any acid! There is no way you can get an SN1 substitution with amines on normal secondary alkyl halides and I wish you could provide a reference if you know about any such example. Only tertiary alkyl halides and some alkyls stabilized by resonance can participate in SN1 reactions in neutral or basic media. You would need the presence of a very strong acid, AlBr3 for example, to get something resembling a carbocation, but only transiently resembling. And obviously this is not possible in the presence of such nucleophiles like the amines because they are too basic. I could find no examples for your suggestion of using (iso)bornyl bromide derived Grignards in a Kumada coupling, but there are some examples of Kumada, Suzuki and Stille couplings using Grignard reagents on norbornyl bromides (that is similar, but in the reversed role of reaction partners, from what you proposed).

I am sorry to disappoint you, Nicodem, but I must believe the evidence before my eyes, in the form of the authoritative organic textbooks, such as Solomons, McMurry, Morrison & Boyd, Bruice, etc., that I have before me. Aliphatic secondary halides, especially bromides of a fairly large structure like that one in question which provide some steric support for dissociation, DO undergo slight dissociation to form carbocations in aprotic polar solvents in equilibrium with the undissociated form, although of course the degree of dissociation is much less than that of tertiary halides (especially tertiary halides in which the resulting positive charge is delocalized by resonance as in triphenylmethyl(+)). And, moreover, the same textbooks indicate that the degree of dissociation, though small, IS quite sufficient, by shifting the equilibrium, for the resulting carbocations to quantitatively bond by electrophilic addition to the N atoms of amines to form substituted amine halide salts. I simply cannot understand why you should think otherwise. The same would apply to electrophilic addition to oxo-compounds to result in oxonium salts, and similarly sulfonium salts. The equilibria in favor of carbocation formation, and hence reaction rates, can be improved by catalytic use of Lewis acids such as AlBr3 or FeBr3.

BTW the C atom to which the Br atom is bonded in 2-bromo-1,7,7-trimethylbicyclo[2.2.1]heptane is, as in borneol, asymmetric (chiral) and optically active; and it is not clear from the illustration provided which enantiomer is the one in question. The one in which the dimethylated bridge is closer to the Br atom would undergo the greater degree of dissociation, and thereby react faster.

[Edited on 11-9-09 by JohnWW]

Nicodem - 11-9-2009 at 04:08

Quote: Originally posted by JohnWW

And, moreover, the same textbooks indicate that the degree of dissociation, though small, IS quite sufficient, by shifting the equilibrium, for the resulting carbocations to quantitatively bond by electrophilic addition to the N atoms of amines to form substituted amine halide salts. I simply cannot understand why you should think otherwise. The same would apply to electrophilic addition to oxo-compounds to result in oxonium salts, and similarly sulfonium salts. The equilibria in favor of carbocation formation, and hence reaction rates, can be improved by catalytic use of Lewis acids such as AlBr3 or FeBr3.

I'm not saying that SN1 based reactions on bornyl bromide is not possible. Like I already said, they could (and actually should) be possible but only under acidic conditions. It is true that the bornyl carbocation is somewhat more stabilized than a normal secondary carbocation (due to hyperconjugation over the ring structure), but still not as much as tert-carbocations are. I searched CA and Beilstein and could find no reactions of bornyl halides&alcohols&esters with amines. The only SN1 based reactions with N-nucleophiles found, were several examples of the Ritter reaction on bornyl alcohols (which are often acompanied by rearrangement to camphene system) and the reactions of bornyl alchols&chlorides with a mixture of aniline&aniline salts. Both are reactions in acidic media. The reaction or bornyl alcohols and bornyl chlorides with anilines is low yielding and also gives a large amount of camphene and tricyclene as side product, thus indisputibly indicating an SN1 mechanism (ref: Journal fuer Praktische Chemie, 322, 423-428; Chemische Berichte, 43, 3204; DE205850). However, I could find absolutely no examples of SN1 based reactions in basic media. So I still say that the reaction of bornyl bromides with amines can not give bornyl amines because the SN2 mechanism is practicaly unavailable due to deactivating factors, while the SN1 mechanism requires acidic media in which aliphatic amines are not nucleophilic any more (and is thus limited to anilines and perhaps some other amines of low basicity, the salts of which are acidic enough to catalyse the reaction). The topic of SN1 based reactions in neutral and basic media trully interests me and my request for an example of a reaction of the type you describe is still valid. I searched for almost an hour and could find none.

Sedit - 11-9-2009 at 12:02

Can anyone suggest a method of deploymerizing PVC or CPVC to yeild Vinylchloride or much better yet 1-2-Dichloroethane since that will be the target compound anyway. I have been reading up but as of yet all I have found it methods that require supercritical water and/or strange conditions of high heats and pressure.

JohnWW - 11-9-2009 at 13:36

Depolymerization - in general, this is difficult, if not impossible, given that most polymerization reactions are exothermic and probably also involve an increase in entropy. However, those that involve acid or alkaline hydrolysis of polyesters (including polycarbonates) or polyamides (including nylons and proteins), in which strongly polar groups provide the linkages, are quite feasible. But such methods would generally not apply to other types of polymers formed in different types of reactions such as condensations of unsaturated monomers or free-radical reactions, e.g. polyethylene, or related polymers of other monomers derived from ethylene or acetylene, such as those of propylene, vinyl chloride or fluoride or acetate, or tetrafluoroethylene.

The methods described for the latter types of polymers in http://en.wikipedia.org/wiki/Thermal_depolymerization generally involve hydrous anaerobic pyrolysis; and the products are not the original monomers but instead simply substances of lower molecular weight - oligomers, like light crude oil.

[Edited on 12-9-09 by JohnWW]

entropy51 - 11-9-2009 at 14:30

Polystyrene and Polymethylmethacrylate can be decomposed by pyrolysis and the monomer distilled out.

Sedit - 11-9-2009 at 17:39

I thought about that myself John and all I could come up with is something that exploited the Cl in a way to aid in cracking the chain. Its all in the mental what if stage at the moment but being a plumber that generates a good deal of PVC, CPVC and ABS waste why not attempt to make use of it. My goal is Dichloroethane but it appears from the most recently reviewed text that many can be depolyermized to various simple organic acids and such. This even though its not what I was looking for is great news. Oxalic acid from PVC and Acetic acid from PP are just to name a few.

entropy51 - 11-9-2009 at 17:47

Sedit, you should be able to buy oxalic at the hardware store as "wood bleach" cheaper than you can make it. Considering that you plumbers charge $89 per hour.

Sedit - 11-9-2009 at 18:32

89$ an hour LMAO we got done doing existing jobs along time ago... If you think we only make 89$ an hour your outcha friggin mind

. All new construction baby everything else is a waste of time and people in your way.

Either way yes I have about 500grams of Oxalic acid extracted from Bar cleaner a while back so its of no real concern but its still a great idea to take a look at the reference section and look at the paper that DJF just provided. Im sure you may find something of use in that mess of simple organics one can get from simply heating +catalyst of scrap plastics which are every where on to large a scale as it is. Perhaps if us amatures started recyling we could get a better rep then we have right now.

not_important - 11-9-2009 at 18:47

PVC, PVA, and similar don't neatly depolymerise, on heating PVC and CPVC mostly give HCl and highly unsaturated tars which break down under further heating. Heating with metal oxides usually gives the chlorides or oxychlorides of the metals and organic gorp along with some carbon oxides.

As already said polystyrene and the polyacrylic esters do depolymerise well. ABS does give its monomers to some degree and a fair amount of gorp and char. Wood gives 3 to 5 percent each of acetic and formic acids, depending on the type of wood, and some methanol.

Polyesters such as PET/PETA, and the polyamides such as nylons, undergo alkaline hydrolysis, some nylons hydrolise nicely with strong acids. Polyurethanes can be hydrolyised as well, but many give a complex mixture of their basic components that isn't terribly useful.

Ethylene glycol may be the easiest OTC route to oxalic acid and 1,2-dichloroethane.

Sedit - 11-9-2009 at 18:56

Bromination to 1,2-dibromoethane from Ethylene Glycol was the plan to begin with but if I could get 1,2-Dichloroethane with ease on the cheep Im all ears. It don't appear to be the case but I will still keep searching to see what I can dredge up. The last ref was interesting so I kind of want to see what more is instore for these plastics.

[Edited on 12-9-2009 by Sedit]

Nicodem - 11-9-2009 at 22:52

I suggest you to focus on bromination of ehtylene glycol with HBr or NaBr/H2SO4.
There is no simple way to 1,2-dichloroethane from vinyl chloride (which is a hazardous gas!) and there is even less chance of a feasible depolimerization of PVC. Besides, 1,2-dichloroethane is a very common industrial solvent (for some reason they use it instead dichloromethane where ever possible - maybe it is cheaper on the bulk?). It is a bit less common solvent in the research labs, but still there is no reason why you would not just order it from a chemical supplier. It is not restricted, it is not suspicious in any way, and it is cheap. However, I would still prefer if you would go the amateur route and do your own 1,2-dibromoethane from ethylene glycol, and post the experience.

1281371269 - 12-9-2009 at 10:13

When distilling out ethanol such that it drips into a beaker, do I risk the majority of it being lost by evaporation? Do I need a closed apparatus, or will sitting the beaker on some ice suffice?

12AX7 - 12-9-2009 at 10:16

Ethanol doesn't evaporate all that fast. As long as it's cold from the condenser, it'll stay in place. Heck, moonshiners often use a bucket for the reciever.

Tim

1281371269 - 12-9-2009 at 10:20

Thanks

Formula409 - 12-9-2009 at 18:06

I'm after some properties on the following compound (vapour pressure, boiling point, melting point, density): 3-chlorobut-2-en-1-ol

The only information I can find is "predicted information", obviously not suitable if one is using it for school work: http://www.chemspider.com/Chemical-Structure.9979359.html

Thanks in advance
Formula409.

497 - 12-9-2009 at 19:24

Why is it that alkylation of tryptamine via routes like these do not alkylate the indole ring nitrogen?

Also would an methylation like this be able to avoid methylating the indole ring nitrogen?

ketel-one - 12-9-2009 at 21:02

What is indole? Benzene ring fused to pyrrole ring. Pyrrole is aromatic so doesn't get alkylated obviously.

ammonium isocyanate - 12-9-2009 at 22:29

Quote: Originally posted by ketel-one

What is indole? Benzene ring fused to pyrrole ring. Pyrrole is aromatic so doesn't get alkylated obviously.

What are you talking about? Firstly, aromatic compounds, including indole, can be alkylated. Secondly, he's asking about the nitrogens on the compounds being alkylated. The nitrogen on indole has only to N-C bonds and can be alkylated just fine if deprotonated with a strong base.

ketel-one - 12-9-2009 at 22:44

Yes, but look closely at the structure. There's an aromatic pyrrole ring hidden in there.

ammonium isocyanate - 12-9-2009 at 22:53

Yes, indole is aromatic. This is true. And also completely irrelevent to 497's question. As I said, indole can be alkylates, even though it's aromatic. Including at the N position, because the nitrogen atom has only two N-C bonds for all intents and purposes. Why the special focus on the aromatic pyrrole ring? The benzene ring is aromatic too.

ketel-one - 12-9-2009 at 23:10

Ammonium, I love you with all my heart. But I am dumbfounded by your responses.

Quote:

Why the special focus on the aromatic pyrrole ring? The benzene ring is aromatic too.

Forget about the benzene, it's not getting alkylated any time soon, nor does it have any reason to.

Quote:

As I said, indole can be alkylates, even though it's aromatic. Including at the N position, because the nitrogen atom has only two N-C bonds for all intents and purposes.

For all intensive purposes, there's two N-C bonds most of the time. Sometimes there's three. It's called resonance, because as we agree pyrrole rings are aromatic.

ammonium isocyanate - 12-9-2009 at 23:27

Sorry if I wasn't clear with my response. The reason I threw that comment about the benzene ring in was because it sounded to me as if you were saying that indole was aromatic solely because of the pyrrole ring. Again, sorry for the misunderstanding.

Yes, I'm aware of the effect of resonance. However, the nitrogen on the pyrrole ring can be alkylated just the same, after all there's a hydrogen on it that could just as well be an alkyl group. And so in the end, the possibility of 3 N-C bonds in the pyrrole ring is a moot point, as it behaves as having 2 all the time (unless you want to drag pKa into this).

ketel-one - 12-9-2009 at 23:42

No it's my fault I wasn't completely correct in what I was saying.

I figured it out, it's not that pyrrole resonates all that much, just that the nitrogen bond with hydrogen is a bit "delocalised" making it harder to alkylate. But I guess it is possible and may be a by-product of whatever 497 was saying.

bbartlog - 13-9-2009 at 12:10

Do solutions of salts that form crystalline hydrates typically form more stable supersaturated solutions (ones that are less likely to spontaneously crystallize)? E.g CuSO4 (pentahydrate), Na2SO4 (decahydrate), FeCl2 and so on...

Pine terpenes

Paddywhacker - 13-9-2009 at 12:22

alpha pinene reacts with dry HCl by addition and rearrangement, or by free radical ... I don't know ... to give bornyl chloride.

Where I live, New Zealand, the local pine oil is, apparently, mostly beta-pinene. What is the reaction mechanism and what is the equivalent reaction with beta-pinene?

Thanks.

JohnWW - 13-9-2009 at 16:05

Just as a matter of interest, how would that ratio of B-pinene to A-pinene and other terpenes in New Zealand pine needle oil, which I presume is from the very common Pinus Radiata, or Monterey Pine, as distinct from other species, compare with that obtained from trees of the same species in their home areas of Monterey, California, and Isla dos Cedros, México? What variation with climate is observed? What about such trees grown in plantations in Chile, South Africa, and Australia, where the species has also been introduced for timber?

If you are talking about addition of HCl or other halo-acid across a double bond on an hydrocarbon such as that in A-pinene, the Markownikoff rule (1869) would usually be observed, i.e. the H attaches to the carbon that has the fewer alkyl substituents, and the halide attaches to the C with the more alkyl substituents. A mixture of products may occur when both unsaturated C atoms are equally alkyl-substituted.

http://en.wikipedia.org/wiki/File:Beta-pinen.png
http://upload.wikimedia.org/wikipedia/commons/thumb/7/77/Alp...
http://en.wikipedia.org/wiki/File:Alpha-Pinene_Isomers.svg
File_Beta-pinen.png - 42kB

[Edited on 14-9-09 by JohnWW]

DJF90 - 13-9-2009 at 16:20

I ran a xfire search on this when another member asked about alkylation using bornyl bromide I think... Anyways it appeared that both alpha AND beta pinene give the SAME (major) product with HBr, with relative stereochemistries (is this a word?) dependant upon that of the starting material. At least if I remember correctly

1,2-Dibromoethane

Sedit - 13-9-2009 at 17:10

1,2-Dibromoethane can be made by the halogenation of Ethylene glycol but I was woundering if there was anything stoping cheep hardware store HCl from performing a simular operation albeit lower yeilding. Lower yeilds from a monetary perspective would be acceptible seeing as batch size could be scaled considerably because I only have 56 grams of NaBr left with 15 grams or so going towards another project. I considered using NaCl+H2SO4 but then got to thinking if it would work in solution as it is.

Anythoughts?

ammonium isocyanate - 13-9-2009 at 19:30

HCl would probably work if in the presence of AlCl3 as a promoter. I'm not sure if all that water is a problem or not.

Sedit - 13-9-2009 at 19:36

The H2O proved to help a bit when I performed the Ethylbromide synthesis by keeping the HBr in solution. Due to HCls lesser solubility its level of fuming can be a bit higher but I don't think the H2O should get in the way of the reaction other then slowing it down to a minor extent due to dilution. AlCl3 seems like a bit much for performing such a synthesis and a simple copper halide catalyst IIRC should work easier then having the need for AlCl3.

ammonium isocyanate - 13-9-2009 at 20:20

Since water isn't a concern you would be using hydrated AlCl3, which is really easy to prepare so you might as well, as IIRC it's the method used in industry and so probably better in some way.

Paddywhacker - 13-9-2009 at 20:54

Quote: Originally posted by JohnWW

Just as a matter of interest, how would that ratio of B-pinene to A-pinene and other terpenes in New Zealand pine needle oil, which I presume is from the very common Pinus Radiata, or Monterey Pine, as distinct from other species, compare with that obtained from trees of the same species in their home areas of Monterey, California, and Isla dos Cedros, México? ....

Yes, it is Pinus radiata in New Zealand, but the Wiki does not mention that species as being used elsewhere. I have read somewhere that the local turpentine has more beta than alpha.

Quote: Originally posted by JohnWW

What variation with climate is observed? What about such trees grown in plantations in Chile, South Africa, and Australia, where the species has also been introduced for timber?

If you are talking about addition of HCl or other halo-acid across a double bond on an hydrocarbon such as that in A-pinene, the Markownikoff rule (1869) would usually be observed, i.e. the H attaches to the carbon that has the fewer alkyl substituents, and the halide attaches to the C with the more alkyl substituents. A mixture of products may occur when both unsaturated C atoms are equally alkyl-substituted.

http://en.wikipedia.org/wiki/File:Beta-pinen.png
http://upload.wikimedia.org/wikipedia/commons/thumb/7/77/Alp...
http://en.wikipedia.org/wiki/File:Alpha-Pinene_Isomers.svg
[Edited on 14-9-09 by JohnWW]

Thanks for the effort with the links, but they don't add any information to that provided by the link that I supplied. The reaction I asked about involves the opening of a four membered ring and the formation of a five membered ring. Involking Markownikoff does not do it justice.

Nicodem - 14-9-2009 at 01:13

@Paddywhacker: It is just a normal carbocation rearrangement. The electrophilic addition of a proton on either alpha- or beta-pinene gives the same product due to thermodynamic reasons (lower energy carbocation forms; or what used to be called the Markownikoff rule in the old, premechanistic times). The carbocation then rearranges via a 1,2-shift* to the bornyl carbocation which is then quenched by the nucleophile (Cl(-), Br(-), H2O, etc.) to give bornyl chloride/bromide/alcohol/etc. This 1,2-shifts in carbocations originating from terpenes is commonly called the Wagner-Meerwein rearrangement** (or the Nametkin rearrangement when only a methyl group shifts). There are numerous such transformations of terpenes and terpenoids known. For example, the pinenes first rerarange to bornyls which further rearrange to camphenes. The electrophilic addition of electrophilies other than a proton can also induce the same rearrangement.

*
http://en.wikipedia.org/wiki/1,2-rearrangement

**
http://en.wikipedia.org/wiki/Wagner-Meerwein_rearrangement
https://themerckindex.cambridgesoft.com/themerckindex/NameRe...

@Formula409: Which one of the two 3-chlorobut-2-en-1-ols? I will not even bother looking for information unless you start to specify which information and about which compound. You have already been told not to name or draw compounds in an ambiguous way.

@Sedit: Nucleophilic chlorination of alcohols with HCl proceeds way slower than the analogous bromination. It would be a waste of time to try the same reaction with HCl, at least without an autoclave. Besides, in case you need 1,2-dibromoethane for SN2 based reactions, you should know that 1,2-dichloroethane is quite unreactive in comparison. It is also much more volatile, thus making isolation and storage more annoying (but less toxic).

ketel-one - 14-9-2009 at 21:45

I was pleasantly surprised today. I put some vodka in a glass in the freezer. I was expecting it not to freeze at all since ethanol is kind of an antifreeze. But it made a sort of clean ice slurry with soft white ice in ethanol. Good way to make ethanol?

Jor - 16-9-2009 at 02:02

I am going to buy oxalyl chloride and Rhodamine B to make chemiluminescence using diphenyloxalate. Do I really need triethylamine to scavenge the formed HCl when reacting oxalyl chloride wiith phenol? I'd rather not buy it. And I don't want to use my pyridine for that purpose, as I only have 25mL of that.

Klute - 16-9-2009 at 02:19

I think you can use excess anhydrous K2CO3 as a substitute, i've done this for acylations and alkylations of amines with great results, whereas the original procedure called for an double equivalent of amine or Et3N. But oxalyl chloride might be reactive enough to directly react with the carbonate.. Considering the price of this reagent it's best to avoid lossing some with side reactions..

If you use excess phenol, and apply slight vacuum, you could remove the formed HCl and drive the reaction forward. But I think that even without removing the formed HCl the reaction will be more or less complete anyway.

But triethylamine is dirt cheap, and very usefull, why not get just 100-250ml of it? It's a very versatil product in org. chem.. You can also prepare PTC's from it, etc

woelen - 16-9-2009 at 03:25

Probably ethylene diamine or diethyl amine can be used equally well for taking away the HCl. Just any amine, which can form salts with HCl will do the job.

Klute - 16-9-2009 at 03:34

Hum, no I don't think it would be wise to use a primary or secondary amine here, as it will get acylated. Amines are more nucleophilic than phenols at neutral pH..

crazyboy - 16-9-2009 at 18:31

If a text says "dissolve X grams of formaldehyde in methanol" that would mean adding enough 37% soln. to methanol to equal X grams correct? It doesn't mean dissolve the gas in methanol somehow?

Sedit - 16-9-2009 at 19:10

@Crazy
If it calls for X grams just make sure the concentration equals 37% how ever you may get there. Just adjust for it if your using a more dilute solution of formaldahyde.

OK I just a quick question that arises from just playing around and for once it appears to be going how I assumed atlest to some extent.

The results of Mixing NaOH + NaNO3 + Al produced ammonia if the temperature was allowed to go to high (expected).

Is my assumption that below 60C that Nitrites should be the product correct?

crazyboy - 16-9-2009 at 20:51

Quote: Originally posted by Sedit

@Crazy
If it calls for X grams just make sure the concentration equals 37% how ever you may get there. Just adjust for it if your using a more dilute solution of formaldahyde.

Well the text didn't specify any concentration it just said add X grams. 37% just happens to be the concentration I can get formaldehyde in.

Klute - 17-9-2009 at 02:29

Hum, I think that refers to anhydrous formaldehyde, not the aqueous solution, overwise it would have be specified IMHO, as formol, formaldehyde solution, 37% formaldehyde, etc. The term "dissolve" refers to bubbling the gas in methanol IMHO.

If you don't have paraformaldehyde, to generate dry formaldehyde gas, you can make it by vacuum distilling the water out of 37% formol, under take off nearly ceases. Then you get a viscous colorless oil, that upon cooling whitens and solififies to paraformaldehyde. Be prepared to pour the still hot residu on a cold surface and break it the rubbery lumps before they solidify to much, as it forms very hard blocks, nearly impossible to break up or grind when hard. But in your case you can just add a few drops of H2SO4 to the residu in your flask, and then heat that up to depolymerise the paraformaldehyde and generate dry formaldehyde gas, dry over P205, and dissolve in your methanol.

Hey, maybe even heating paraformaldehyde in methanol with a drop of H2SO4 could depolymerise it.. I think bases are more efficient at depolyerising paraformaldehyde, so a catalytic amount of alkali methoxide in your methanol could depolymerise the paraformaldehyde. Have a look on the net to see if you find any info on this..

EDIT: I'm even asking myself if the term formaldehyde doesn't refer to paraformaldehyde here, perhaps simply adding paraformaldehyde to methanol can depolymerise it, forming the hemiacetal, or perhaps acetal, of formaldehyde and methanol..

EDIT2: found this:

"In the presence of small amounts triethylamine, paraformaldehyde dissolves in methanol already at 45° to 50° C. At reflux conditions, one obtains a complete solution in 5 to 10 minutes."
http://www.freepatentsonline.com/4237065.html

surely it's depolymerising here.

and this:

"It dissolves readily in water or alcohol by hydrolysis or depolymerization to yield free formaldehyde"
http://www.wipo.int/pctdb/en/wo.jsp?IA=US1997004396&DISP...

[Edited on 17-9-2009 by Klute]

[Edited on 17-9-2009 by Klute]

entropy51 - 17-9-2009 at 06:09

I don't know what syn you are using the HCHO in, but paraformaldehyde is often used directly instead of bubbling in anhydrous HCHO as a gas. I have used paraformaldehyde directly in Blanc chloromethylations and as a solution in THF for reaction with Grignards.

Jor - 17-9-2009 at 06:50

I am soon attempting the luminol synthesis. However, for the last step you need sodium dithionite, to reduce the nitro-group to an amino-group. I don't have this reagent. Are there alternative reducing agents? Like Sn/HCl?

All procedures describe reacting hydrazine with 3-nitrophthalic acid in high boiling (250C IIRC) triethylene glycol. Would ethylene diglycol also be suitable? Or preferably another solvent?

JohnWW - 17-9-2009 at 07:02

Quote: Originally posted by ketel-one

I was pleasantly surprised today. I put some vodka in a glass in the freezer. I was expecting it not to freeze at all since ethanol is kind of an antifreeze. But it made a sort of clean ice slurry with soft white ice in ethanol. Good way to make ethanol?

Yes, I have heard of cheap rot-gut spirits being made from the liquor of a fermented mix by freezing the water out, instead of distilling the ethanol off and collecting it. However, the spirits obtained by freezing are liable to contain an excessive amount of fusel oil, i.e. higher alcohols and esters, which in the much smaller amounts usually distilled over with the ethanol in the conventional manner impart spirits (especially whiskeys and brandys) with their characteristic tastes and odors. The large amount of fusel oil remaining with alcohol after freezing out the water is, unfortunately, toxic in large amounts.

mr.crow - 17-9-2009 at 07:07

First post time

This is really basic because I am just starting out.

I have a large amount of Sodium Bromide I recrystallized from some pool solution from Wal-Mart. The crystals are beautiful plates, defiantly not salt.

My question is, how do I dry it off? Leave it in a buchner funnel, leave it in the air, or put it in an oven?

Also it appears it forms a dihydrate. Wikipedia says it melts at 34 degrees, so could I heat it in a beaker until it fuses solid? Or just keep it as a dihydrate.

Picric-A - 17-9-2009 at 10:23

Sodium bromide melts at 747 deg C, its dihydrate dehydrates at 34deg C so if you wanted the anhydrous powder keeping it in a 200deg C oven for an hour would leave you with the anhydrous product.

Paddywhacker - 17-9-2009 at 12:13

Quote: Originally posted by Jor

I am soon attempting the luminol synthesis. However, for the last step you need sodium dithionite, to reduce the nitro-group to an amino-group. I don't have this reagent. Are there alternative reducing agents? Like Sn/HCl?

All procedures describe reacting hydrazine with 3-nitrophthalic acid in high boiling (250C IIRC) triethylene glycol. Would ethylene diglycol also be suitable? Or preferably another solvent?

Boiling points
diethylene glycol 244
triethylene glycol 285
glycerol 290 (with decomposition?)

so, no.

[Edited on 17-9-2009 by Paddywhacker]

Picric-A - 17-9-2009 at 12:16

Quote: Originally posted by Paddywhacker

Quote: Originally posted by Jor

Is this is question? if so, yes glycerol works, i have used it successfully before.
As for the reducing agent i tryed Zn/HCl method but it failed to produce any luminol. I also have no access to Na2S2O4

[Edited on 17-9-2009 by Picric-A]

entropy51 - 17-9-2009 at 13:23

There is an OTC product which consists mainly of sodium dithionite and carbonate. I don't know about the luminol synthesis, but it works for a number of other purposes.

Rit Color Remover http://www.ritdye.com/Fabric+Treatments.28.51.7.49.lasso

Dithionite can also be prepared by reducing SO2 with sodium formate in aqueous methanol. There is a reference posted around here somewhere on this method.

[Edited on 17-9-2009 by entropy51]

1281371269 - 17-9-2009 at 14:02

I just received a joblot of quickfit stuff won on ebay. So that I can work out which bits I need to get, adaptors and so forth, I need to be able to measure the joint sizes where the writing has worn off. I have some tools for woodwork that measure diameters in mm - is the 42/22 rating thing the top of the joint width over the bottom of the joint width in mm?

entropy51 - 17-9-2009 at 14:48

Google is your friend! http://en.wikipedia.org/wiki/Ground_glass_joint

I think you mean "diameter" rather than "width".

watson.fawkes - 17-9-2009 at 15:22

Quote: Originally posted by entropy51

Google is your friend! http://en.wikipedia.org/wiki/Ground_glass_joint

Yes, but the description there is slightly lacking, as it has no table of standard sizes. See http://www.wilmad-labglass.com/pdf/taper_ground_joint_dims.pdf for a solid drawing with tables standard dimensions. The modern standard is ASTM E676, which costs to acquire. Original dimensions are from NIST CS21-58, now withdrawn.

crazyboy - 17-9-2009 at 16:38

Quote: Originally posted by Klute

Hum, I think that refers to anhydrous formaldehyde, not the aqueous solution, overwise it would have be specified IMHO, as formol, formaldehyde solution, 37% formaldehyde, etc. The term "dissolve" refers to bubbling the gas in methanol IMHO.

If you don't have paraformaldehyde, to generate dry formaldehyde gas, you can make it by vacuum distilling the water out of 37% formol, under take off nearly ceases. Then you get a viscous colorless oil, that upon cooling whitens and solififies to paraformaldehyde. Be prepared to pour the still hot residu on a cold surface and break it the rubbery lumps before they solidify to much, as it forms very hard blocks, nearly impossible to break up or grind when hard. But in your case you can just add a few drops of H2SO4 to the residu in your flask, and then heat that up to depolymerise the paraformaldehyde and generate dry formaldehyde gas, dry over P205, and dissolve in your methanol.

Thanks, you're absolutely right a few hours after I posted that it hit me it has to be anhydrous because the next step is sodium borohydride reduction.

So once I get paraformaldehyde how can I generate formaldehyde gas?

kclo4 - 17-9-2009 at 19:59

paraformaldehyde can be decomposed by an acid or heating IIRC.
http://en.wikipedia.org/wiki/Paraformaldehyde#Reactions

Wiki agrees

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