Ch_322b_16.13

Ch_322b_16.13 - Catalytic hydrogenation of aldehydes and...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Reductions of Carbonyl Compounds. A Review Aldehydes are reduced to primary alcohols and ketones are reduced to secondary alcohols by a variety of reagents. In general, alcohols and aldehydes/ketones are readily interconverted. RCHR' OH [O] [H] RCR' O = Metal Hydrides Lithium aluminum hydride (LiAlH 4 ) and sodium borohydride (NaBH 4 ) reduce aldehydes and ketones to alcohols. O LiAlH 4 H OH (i) (ii) workup cyclohexanone cyclohexanol CH O NaBH 4 (i) (ii) workup CH 2 OH benzaldehyde benzyl alcohol
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Metal Hydrides as Hydride Transfer Agents LiAlH 4 and NaBH 4 reduce carbonyl compounds by transferring hydride , H: - , as a nucleophile to the electropositive carbon center., C O = ! + !" M H H H H - group 3 metal hydride hydride transfer ~H: - C H O MH 3 - C H O M - 4 4 equivalents of hydride C H O M - 4 workup H 3 O + C H O H alcohol
Background image of page 2
Catalytic Hydrogenation of Carbonyl Compounds
Background image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Catalytic hydrogenation of aldehydes and ketones occurs, but is usually a second choice after metal hydride reduction. Alkenes and alkynes typically hydrogenate faster, while esters (RCO 2 R') and carboxylic acids (RCO 2 H) hydrogenate much slower, than aldehydes and ketones. general reactivity order in catalytic hydrogenation A AH 2 Pt/H 2 RC CR' > RR'C=CR''R''' > RCCl O = > RCH (R') O > RCOR' O > RCOH O very fast very slow Sometimes catalytic hydrogenation is a useful procedure because it reduces more than one functional group in a compound. 2 CH 3 CH O aldol condensation CH 3 CH=CHCH O 2-butenal H 2 Ni CH 3 CH 2 CH 2 CH 2 OH 1-butanol...
View Full Document

This note was uploaded on 10/20/2009 for the course CHEM 322BL at USC.

Page1 / 3

Ch_322b_16.13 - Catalytic hydrogenation of aldehydes and...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online