making acetic anhydride

[dom3mo]

Can anyone tell me how to make acetic anhydride by dehydrating acetic acid.

[Tartaglia]

Would P4O10 not work

[dom3mo]

i am not sure

[Aaron_S]

Maybe sulfuric acid? or just heating to about 800-900*C?

[al93535]

If you concentrate (dehydrate) acetic acid you will simply have concentrated acetic acid, or glacial acetic acid. Its impossible to make acetic anhydride from acetic acid. They are two different chemicals, not simply a diluted solution.

[hermanntrude]

because they're different chemicals you can't make one from the other? Oh dear... there goes all chemistry. I suspect the name "acetic anhydride" comes from the fact that i's what you get when you remove water from acetic acid.

 

You are correct that if you remove water from a solution of acetic acid you'll just get a more concentrated solution, but if you remove water from the molecule you end up with an anhydride.

 

Some breif research on the net gave me this:

 

As the name indicates, an acid anhydride is a compound that is related to an acid by the loss of water. Acetic anhydride can by prepared by the dehydration of acetic acid at 800°C.

 

Alternatively, the reaction between the acid chloride and a salt of acetic acid (e.g. sodium acetate) yields acetic anhydride and a salt.

 

 

source

[dom3mo]

ok thanks i'll just go with the chloride, and sodium acetate way.

[nitric]

easier, in theory, just dehydrate glaceil acetic acid with concentrated H2SO4

[hermanntrude]

usually the less harsh the conditions you use the easier the mess is to clean up afterwards. H2SO4 is notorius for creating a thick oily mess of by-products instead of any useful products. It's also usually impure.

[nitric]

like the dehydration of sugar, but if he cant find a good heating source, second easiest way

[hermanntrude]

i'm really not sure sulphuric will work. I know you love the chenistry which involves the nastiest most hazardous substances you can get hold of, but there's no need to start telling the rest of the world to burn their eyes out too.

[nitric]

im not stating that, but to keep on track i would recomend that you go with the high heat dehydration, seems cleaner and more reliable, but it would require most likely a tube furnace(not so sure though), bunsen burner i think only reaches up to about 675*C

[John Cuthber]

im not stating that, but to keep on track i would recomend that you go with the high heat dehydration, seems cleaner and more reliable, but it would require most likely a tube furnace(not so sure though), bunsen burner i think only reaches up to about 675*C

 

A bunsen flame gets a lot hotter than that.

[hermanntrude]

depends on the bunsen and the pressure of the gas. the ones in my lab reach about 700°C

[YT2095]

the yellow "safety" flame is about 1000c, you can add a couple of hundred extra for the blue flame.

[nitric]

is that calories or celsius, because ive never heard of a 1000*C saftey flame, least bunsen burner flame

 

http://www.mr-damon.com/experiments/bunsen/index.htm

it says that the roaring blue flame is 700*C

Edited November 26, 2008 by nitric
found something

[hermanntrude]

i'm fairly sure the temperature depends on several factors, including the design of the bunsen itself.

[slow]

suppose heating to 800 c is not a problem. the applications that call for AA suggest that it is in a liquid form. how do you then return the dehydrated AA to a liquid when it reacts with H2O converting itself back into acetic acid. What liquid should be used for re hydration?