Sciencemadness Discussion Board - esters!

esters!

Lithium - 25-2-2012 at 22:13

hello

i, and probably many of you, like esters.

i have hit a fork in the road in terms of synthesis.

i know of three routes:

acid anhydride and alchohol react to respective ester and H2O

acid halide and alchohol react to form respective ester and HX

X= halide

carboxylic acid and alchohol react in presence of H2SO4 to form respective ester and H2O

i have no access to acid anhydrides or chlorides, nor do i want to use all of my precious H2SO4 that i don't have.

any thoughts much appreciated,

Lithium

(sorry if i missed a thread about this somewhere else)

Lithium - 26-2-2012 at 03:15

Damn, 2 in 1 minute.

this must really p**s you off how you have to keep moving all these threads, i'm sorry for annoying you

[Edited on 26-2-2012 by Lithium]

Hexavalent - 26-2-2012 at 07:52

How much H2SO4 do you have? For most reactions, it is only needed to protonate the alcohol to increase its eletrophilicity and thus is catalytic - in most cases, only a few drops to 20ml is needed. You can even use hardware store variety acid . . .

Lithium - 26-2-2012 at 11:25

i have no H2SO4 and have never seen it in the store, would NaHSO4 or H3PO4 work? they are both quite acidic.

i could order sulfuric acid off ebay, but it would take weeks, perhaps ill buy some this weekend.

Li

[Edited on 26-2-2012 by Lithium]

[Edited on 26-2-2012 by Lithium]

Hexavalent - 28-2-2012 at 13:02

I doubt that phosphoric acid would work in a lot of cases as it is a comparatively weak acid. The purpose of an acid, if you'd bothered to read the mechanism for say, a Fischer Esterification, is for a protonation for nucleophilic attack. Thus, there is a chance that your carboxylic acid would be stronger than the H3PO4, and the former would protonate the latter . . .thus completely ruining the reaction.

Just get some sulfuric acid at any cost - it is one of the main essentials of a home lab IMO, as well as hydrochloric acid, nitric acid, sodium hydroxide/potassium hydroxide, sodium carbonate and a few other salts.

neptunium - 28-2-2012 at 13:20

agree! without sulfuric acid there isnt much you can do its a fantastic acide for many chemical reaction! in fact a country economy is directly linked to its sulfuris acide production..
so you can get H3PO4 and not H2SO4?? weird !
the phosphoric is usually my problem!

get it from ebay there is a guy in Nebraska saling it for about 10 or 12 bucks 950ml its not food grade but its 98% and does the job nicely. never had a problem with it

[Edited on 28-2-2012 by neptunium]

GreenD - 28-2-2012 at 13:30

amazon.com

entropy51 - 28-2-2012 at 16:49

Quote: Originally posted by GreenD

amazon.com

Lithium is apparently located in Australia which raises problems in shipping and customs. There is certainly no problem getting it in the United States. I recently bought a liter for about $12 with no hazardous shipping charges.

neptunium - 28-2-2012 at 17:18

its not the first time i read about a home chemist having troubles acquiring chemicals in Australia , i think there is even a topyc on it....hope it never gets like that here in the US!

Lithium - 28-2-2012 at 23:07

yes, i am from aus, and me and weiming1998 have been discussing this dilemma in the buying chemicals in western australia thread.

i am still unsure if i will get in trouble if i order some H2SO4 from ebay.

i have seen people use HCl as a catalysing acid, though that's only in their theory work.

i get my H3PO4 from a specialist beer brewing shop.

funnily enough, it is easier for me to get elemental iodine rather than sulfuric acid!

oh well

Li

[Edited on 29-2-2012 by Lithium]

phlogiston - 29-2-2012 at 14:40

It must be available nearly everywhere as battery acid. It is my only source too. Here (the Netherlands), every car parts store sells it. I believe the concentration is typically around 15%, but it can readily be concentrated if necessary.

[Edited on 29-2-2012 by phlogiston]

bahamuth - 29-2-2012 at 15:19

Quote: Originally posted by phlogiston

It must be available nearly everywhere as battery acid. It is my only source too. Here (the Netherlands), every car parts store sells it. I believe the concentration is typically around 15%, but it can readily be concentrated if necessary.

[Edited on 29-2-2012 by phlogiston]

Lead battery acid is closer to 30% IIRC.

Lithium - 29-2-2012 at 21:13

i tried buying some but they said it would be "too dangerous" for me ( i am 13 )

my parents don't like driving me around to random places all the time.

i am planning on doing the iron sulfate oxalic acid route on large scale ( found some 120L buckets

)

i have 5Kg of (NH4)2SO4, how would i turn this into FeSO4?

i was thinking of Fe(OH)2 or Fe2O3 and using the NH3 somewhere else

what can lots of NH3 be used for?

Li

[Edited on 1-3-2012 by Lithium]

weiming1998 - 1-3-2012 at 00:37

Quote: Originally posted by Lithium

i tried buying some but they said it would be "too dangerous" for me ( i am 13 )

my parents don't like driving me around to random places all the time.

i am planning on doing the iron sulfate oxalic acid route on large scale ( found some 120L buckets

Adding an iron acetate solution (which is created by heating iron/iron oxide and vinegar together in a beaker) to your ammonium sulfate. Boil the resulting mix until crystals start to form. Turn off heat and refrigerate. Filter. Then there will be iron sulfate crystals (with trace ammonium acetate contamination that won't really matter for this purpose)

Lithium - 1-3-2012 at 01:42

thanks! that is a good synthesis, though i imagine i would have to add things together stochiometrically.

i can only imagine the time and effort i would have to put into making a few litres of sulfuric acid

nevertheless, it would be a fun synthesis i could do in the school holidays when i have no overdue homework to attend to

i will just have to hoard the chems needed until that time.

btw, how are you going in your H2SO4 ordeals?

Li

[Edited on 1-3-2012 by Lithium]