Nucleophilic substitution on carbonyl groups carboxylic acid derivatives

Nucleophilic substitution on carbonyl groups carboxylic acid derivatives 

We have seen that most of the addition reactions involving aldehydes and ketones are reversible (see 

Section 7.1.2). If the anionic intermediate does not react with an electrophile, then the carbonyl group is reformed and the original nucleophile is lost, i.e. it becomes a leaving group. 

However, if there is another leaving group in this molecule, then this may be lost instead, so that overall the reaction becomes a nucleophilic substitution, though really it should be regarded as an addition-elimination sequence, since the 

Acetyl chloride must always be stored under anhydrous conditions, because it readily reacts with moisture and becomes hydrolysed to acetic acid. On the other hand, if one wanted to convert ethyl chloride into ethanol, this nucleophilic substitution reaction would require hydroxide, with its negative charge a better nucleophile than water, and an elevated temperature (see Section 6.3.2). It is clear, therefore, that the carbonyl group is responsible for the increased reactivity, and we must implicate 

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NUCLEOPHILIC SUBSTITUTION ON CARBONYL GROUPS CARBOXYLIC ACID DERIVATIVES... 

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