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Post by Aleu on May 14, 2008 18:02:59 GMT -8
Seeing as I'm a total chem dork, and it seems to be a sticking point for more than most, here's a little place where you can drop in whatever questions you might have on the subject. I've got a passably fair knowledge of everything the AP exam overs, plus a lot more orgo, so let 'er rip x3
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Post by Kalphin on May 14, 2008 18:10:59 GMT -8
Heh heh heh, I already did my AP Chem test. Can't trick me Aleu!
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Post by ♫ Busan ♫ on May 14, 2008 18:13:36 GMT -8
Can you give me examples of Aldehyde and esterification reactions?
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Post by Arynielle on May 14, 2008 21:07:35 GMT -8
My AP chem test is over and done with. Now I can wipe all that stuff from my head.
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Post by Aleu on May 15, 2008 1:49:18 GMT -8
Kayo. It's kinda strange for them to be asking you aldehyde synthesis -- it's kinda heady stuff, and from what I can remember I never had to deal with it. However, an aldehyde reaction is one that produces an aldehyde as its end product -- a chemical compound with a carbon at one end double bound to an oxygen, singly bound to a hydrogen, and singly bound to another carbon in the chain. Now, the way to go about doing this is a little strange, but bear with me -- the only method I believe you have to know (if any) is oxidation of an alcohol. The final carbon in an alcohol has C single bound to an -OH group and 2 hydrogens. In an oxidation reaction (oxidation is defined as a loss of electrons, a loss of H+, or a gain in oxygen), the -OH loses its H, and one of the 2 H's gets snapped off, and an oxygen atom from the oxidizing agent combines with the two of them to make water. Now that the carbon and oxygen are both in need of another bond -- pop, there they go, and now you have an aldehyde. www.elmhurst.edu/~chm/vchembook/images3/701synald.jpg/\ That summarizes what I just explained. Their notation is really ugly, because they use H2 instead of drawing in the H's on opposite sides, but I think it's still understandable. The reason I say that this is a little over what I'd expect them to ask of you is that it's not a true synthesis reaction, at least in the context that most AP classes would teach (are you taking IB by any chance?). You only have one organic reagent and it requires an oxidizing component, which is a little bit over the simple dehydration/hydrolysis reactions that you should be doing (it kinda is dehydration but... not in the basic orgo sense ><) Esterification is much easier to explain: an ester is an organic molecule where a carbon -not- on the ends is bound to another carbon (or anything really) in the chain, double bound to oxygen, and single bound to oxygen, single bound to another carbon (or anything) in the chain. Here you can see: R is the first component of the chain, the O is double bound to carbon, the second O is single bound to carbon, and R' is the rest of the chain.How do you make one? React an alcohol with an acid. Let's use a carboxylic acid, since its organic. CH3CH2CH2COOH + CH3CH2OH (that'll be butanoic acid and ethanol -- the stuff that gives beer that happy buzz) The best way to think about this is to whirl it around. CH3CH2CH2COOH + HOCH2CH3 (same molecule, just turned around). Now-- CH3CH2CH2CO OH + H OCH2CH3 See that? That OH and that H turn into water. H2O + CH3CH2CH2CO + OCH2CH3 And that O already has a double bond with the O, so it needs to get its last bond from somewhere else -- that O on the right looks fine. Bonds form, ester made! CH3CH2CH2COOCH2CH3 (Ethyl butyrate) + H2O
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