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Author: Subject: The short questions thread (2)
turd
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[*] posted on 9-8-2009 at 12:44


Quote: Originally posted by Formula409  
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)
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[*] posted on 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?
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[*] posted on 10-8-2009 at 20:51


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



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[*] posted on 12-8-2009 at 12:38


no, to add to alkenes fatty acid you must use the cyanide route.
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[*] posted on 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.





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JohnWW
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[*] posted on 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]

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[*] posted on 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...



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[*] posted on 13-8-2009 at 13:24


No, not if you want it to remain in one piece.
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[*] posted on 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?
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[*] posted on 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.
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[*] posted on 17-8-2009 at 03:16
jones oxidation


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?
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[*] posted on 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.



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[*] posted on 17-8-2009 at 12:35


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




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[*] posted on 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.
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[*] posted on 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
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[*] posted on 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)




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[*] posted on 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]




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[*] posted on 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




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[*] posted on 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.
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[*] posted on 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 (~_~)




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[*] posted on 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)
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[Edited on 8-9-2009 by sonogashira]
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