Esters

· Esters contain the functional group –COO–.
· General ester structure: RCOOR′, where R and R′ are carbon-containing groups.
· In topic 33.2, esters are produced by reacting alcohols with acyl chlorides.
· Key exam idea: acyl chloride + alcohol → ester + HCl.
· This is a fast reaction because acyl chlorides are very reactive carboxylic acid derivatives.
· Exam examples required: ethyl ethanoate and phenyl benzoate.

Phenyl benzoate is an ester with the linkage –COO– joining a benzoyl group to a phenyl group. This is one of the named CIE examples for ester formation from an acyl chloride and phenol. Source

Making ethyl ethanoate

· Reactants: ethanoyl chloride + ethanol.
· Product: ethyl ethanoate + hydrogen chloride.
· Equation: CH₃COCl + CH₃CH₂OH → CH₃COOCH₂CH₃ + HCl.
· The alcohol provides the –OR′ part of the ester.
· The acyl chloride provides the RCO– part of the ester.
· Exam trap: do not confuse ethyl ethanoate with ethyl propanoate or methyl ethanoate.

Ethyl ethanoate has the ester linkage CH₃COOCH₂CH₃. The ethanoyl part comes from ethanoyl chloride, while the ethyl part comes from ethanol. Source

Making phenyl benzoate

· Reactants: benzoyl chloride + phenol.
· Product: phenyl benzoate + hydrogen chloride.
· Equation: C₆H₅COCl + C₆H₅OH → C₆H₅COOC₆H₅ + HCl.
· Phenol acts like the –OH compound reacting with the acyl chloride.
· Key naming point: phenyl benzoate is the ester made from phenol and benzoyl chloride.
· Exam trap: phenyl means the oxygen is bonded to a benzene ring; benzoate means the carbonyl carbon is attached to a benzene ring.

Phenyl benzoate shows the ester group between two aromatic rings. It is formed from benzoyl chloride and phenol, producing HCl as the by-product. Source

Key reaction pattern to memorise

· General equation: RCOCl + R′OH → RCOOR′ + HCl.
· RCOCl = acyl chloride.
· R′OH = alcohol or phenol-type reactant in the required examples.
· RCOOR′ = ester.
· HCl is always formed as the by-product.
· To name the ester: name the group from the alcohol/phenol first, then the carboxylate/acyl part second.
· Example: ethanol + ethanoyl chloride → ethyl ethanoate.
· Example: phenol + benzoyl chloride → phenyl benzoate.

The page illustrates how an acyl chloride reacts with an alcohol to form an ester. For CIE 33.2, focus on the overall reaction pattern and products rather than unnecessary extra detail. Source

Exam wording to use

· “The ester is formed by the reaction of an alcohol with an acyl chloride.”
· “The by-product is HCl.”
· “The ester linkage formed is –COO–.”
· “For ethyl ethanoate: ethanoyl chloride reacts with ethanol.”
· “For phenyl benzoate: benzoyl chloride reacts with phenol.”
· Include structural formulas where possible to show which part of each reactant forms the ester.

This page is useful for comparing how acyl chlorides form esters with alcohols and phenol. The most important CIE 33.2 idea is that the ester forms with HCl as the by-product. Source