8B_handout_feb6

8B_handout_feb6 - Chem 8B, winter 2009, Feb 6 handout...

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Chem 8B, winter 2009, Feb 6 handout (sections 13.7, 16.1-5, 16.8) Reactions of carbonyls with water and alcohol, Intro to carbohydrates Suggested Sample Problems in Chap 13: 10, 13-15,19ab, 20, 27, 28, 31; Chap 11: 22cf, 29cf Water or alcohol can be a nucleophile that will add to an aldehyde or ketone. If water adds, the product is called a hydrate product. With an alcohol, the product is called a hemi-acetal (if one alcohol molecule is incorporated) or an acetal (if two alcohol molecules are incorporated). The addition of an alcohol nucleophile to a ketone is called a ketal product. If a carbonyl is more electrophilic, then it will react faster and form more hydrate or acetal product. For example, an aldehyde is more electrophilic than a ketone so it will have 99% hydrate while a ketone will have less than 1% hydrate. (H + = HCl catalyst) H 3 C H O H + H 3 C H OH OH hydrate H 3 C H O H–OCH 3 H + H 3 C H OCH 3 OCH 3 acetal H 2 O H 3 C CH 3 O H–OCH 3 H + H 3 C CH 3 OCH 3 OCH 3 ketal ketone aldehyde aldehyde Now consider the mechanism of hydrate and acetal formation. Because water and alcohols are weaker nucleophiles than amines and hydride, the mechanism usually requires an acid catalyst. In the first step of the reaction, the acid protonates the carbonyl to make it a better electrophile
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This note was uploaded on 03/12/2009 for the course CHE 8B taught by Professor Lievens during the Winter '07 term at UC Davis.

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8B_handout_feb6 - Chem 8B, winter 2009, Feb 6 handout...

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