User:Benjah-bmm27/degree/1/VKA
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Introduction
[edit]"Reactions and Synthesis with Carbonyl Compounds", Professor Varinder Aggarwal.
General features of carbonyl reactions
[edit]- The carbonyl group is electrophilic at carbon, so many nucleophiles can (and do) attack there
- The mechanisms of these reactions generally involve the following steps:
- A nucleophile adds to the carbon atom of a carbonyl group. This step is called nucleophilic addition.
- The product formed by nucleophilic addition to a carbonyl group is generally a tetrahedral carbonyl addition compound.
- If the tetrahedral product is unstable, it can collapse back to a trigonal carbonyl compound by expelling a leaving group.
- The overall process of nucleophilic addition followed by leaving group elimination is called nucleophilic acyl substitution, because the nucleophile replaces the leaving group as a substituent on the carbonyl carbon.
Particular examples of carbonyl reactions
[edit]- Reduction of aldehydes and ketones to alcohols with sodium borohydride, NaBH4
- Reduction of esters to alcohols with lithium aluminium hydride, LiAlH4
- Jones oxidation: oxidation of primary alcohols to carboxylic acids and secondary alcohols to ketones with chromium trioxide, CrO3 (can also use e.g. pyridinium chlorochromate, PCC)
- Ester hydrolysis, such as saponification
- Alkylimino-de-oxo-bisubstitution
- RCO2H + OSCl2 → RCOCl + HCl + SO2
- goes via an SNi mechanism