C6H5CO

C6H5CO, commonly written as Ph-CO or the benzoyl group, is the benzenecarbonyl substituent derived from benzoic acid. It consists of a phenyl ring (C6H5) bonded to a carbonyl carbon (C=O), giving the substituent Ph-CO-. The neutral fragment has the formula C7H5O and is planar with sp2-hybridized atoms.

In organic synthesis, the benzoyl group serves as a versatile acyl substituent. It appears in reagents such as benzoyl chloride (Ph-CO-Cl) and various benzoyl derivatives used to introduce the carbonyl functionality onto arenes. It participates in Friedel–Crafts acylation to form aryl ketones (for example, benzophenone-type products) and can be used to acylate amines to give benzamides, effectively serving as a protecting or activating group in multistep syntheses.

Properties and reactivity: The benzoyl group is strongly electron-withdrawing, which deactivates the aromatic ring and directs electrophilic aromatic substitution to the meta position relative to the carbonyl. Its chemistry is dominated by transformations of the carbonyl group (acylation, reduction, hydrolysis) and by formation or manipulation of benzoyl derivatives.

Occurrence and preparation: The benzoyl moiety is present in many commercial reagents (for example, benzoyl chloride) and in numerous natural and synthetic compounds. Benzoyl chloride is commonly prepared from benzoic acid using chlorinating reagents such as thionyl chloride.

See also: benzoyl chloride, benzaldehyde, benzoic acid, benzamide, benzophenone.