Organic Chemistry (CHEM 227) Alcohol Reactions – Chap. 17
Acid/Base proton transfer
Reduction of aldehydes yields primary alcohols,
Nucleophilic attack of a hydride forms an alkoxide ion intermediate which, in a second step, is protonated to yield the corresponding alcohol product
Reduction of ketones yields secondary alcohols
Nucleophilic attack of a hydride forms an alkoxide ion intermediate which, in a second step, is protonated to yield the corresponding alcohol product
Reduction of esters yield primary alcohols.
Nucleophilic attack of a hydride followed by elimination of an alkoxide ion yields an aldehyde that on further reduction yields an primary alcohol
Reduction of Carboxylic acids yield primary alcohols
Nucleophilic attack of a hydride on the carboxylate anion gives a high energy dianion intermediate which yields an aldehyde which on further reduction yields a primary alcohols
Aldehydes yields a secondary alcohols
Nucleophilic attack of a Grignard reagent forms an alkoxide ion intermediate which, in a second step, is protonated to yield the corresponding alcohol product
The presence of any other functional group with acidic protons must be avoided
Ketones yield tertiary alcohols
The presence of any other functional group with acidic protons must be avoided
Nucleophilic attack of a Grignard reagent forms an alkoxide ion intermediate which, in a second step, is protonated to yield the corresponding alcohol product
The presence of any other functional group with acidic protons must be avoided
Esters react with two equivalents of Grignard reagents to yield tertiary alcohols.
Nucleophilic attack of a Grignard reagent forms a ketone which on further reaction with a second equivalent of the Grignard reagent forms an alkoxide. This, in a second step, is protonated to yield the corresponding tertiary alcohol product
The formation of the tosylate does not affect the configuration of any existing chirality centers
The displacement of a tosylate in an Sn2 reaction proceeds with inversion of configuration
Phosphorus reacts with a secondary alcohol to form a dichlorophosphate which is a good leaving group
The elimination step is an E2 reaction
Alcohols react with carboxylic acids in the presence of a strong acid to give esters
Sulfuric acid or hydrochloric acid are often used as catalysts
E2 elimination to generate a carbon-oxygen double bond
Primary or secondary alcohols react with several chromium or manganese reagents to yield carboxylic acids or ketones respectively.
Oxidation of primary alcohols with Na2Cr2O7 or CrO3 makes it very difficult to isolate the initial aldehyde; milder oxidizing reagents are preferred for this purpose
E2 elimination to generate a Carbon-Oxygen double bond
Primary or secondary alcohols react with mild oxidizing reagents like Dess-Martin periodinane (DMP) or Pyridinium Chlorochromate (PCC) to give aldehydes and ketones respectively
Alcohols react with a chlorotrialkylsilane, CL-CiR3, in the presence of a base to yield a trialkylsilane ether, ROSiR3.
Reaction of the TMS ether with aqueous acid regenerates the alcohol.
Na2Cr2O7 other milder oxidizing reagents like Ferric Iron (FeCl3) or Silver oxide
Effective reducing reagents are SnCL2, Na2S2O4 (sodium dithionite)
The quinone/hydroquinone equilibrium is electrochemically reversible
Acid catalyzed dehydration of a glycol (a vicinal diol) yields a rearranged carbonyl product. Proceeds through a carbocation intermediate