Organic 2 Review Problem 171

Organic 2 Review Problem 171 - P REPARATIONS 155 Lithium...

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PREPARATIONS 155 Lithium Aluminium Hydride Reductions. Lithium aluminium hydride, LiAlH 4 , is a very active reducing agent, and is used particularly for the ready reduction of carboxylic acids (or their esters) to primary alcohols: R-COOH -> R-CH 8 OH. It will also reduce acid chlorides, acid anhydrides and aldehydes to primary alcohols, ketones to secondary alcohols, and amides to the corresponding amines: R-CONH 8 -»• R-CH 8 NH 2 . Nitro-hydrocarbons if aromatic are usually reduced to azo-compounds, and if aliphatic to primary amines. The C:C bond in aliphatic compounds is usually unaffected, but in aromatic com- pounds the bond may be hydrogenated if it is directly linked to the aromatic nucleus: thus cinnamic acid gives 3-phenylpropan-i-ol: C 6 H 6 CH:CH-COOH -^C 6 H 6 CH 2 CH 2 CH 8 OH. The C : .C bond, unless strongly activated by neigh- bouring groups, is also usually unaffected. Lithium aluminium hydride if carelessly manipulated may be dangerous for
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This note was uploaded on 09/19/2011 for the course CHM 2211 taught by Professor Castalleano during the Fall '06 term at University of Florida.

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