Acetyl-chloride bond angles

Figure 5.26. A representation of ethanoyl chloride (acetyl chloride, H3CCOCI) showing bond lengths and angles (as determined by microwave spectroscopy).

Steric hindrance in flve-membered rings should be less than in benzene because of the different angles between adjacent C-substituent bonds (60° in benzene, 72° for a regular pentagon), which produces a greater distance between adjacent substituents in the former. The importance of this effect is demonstrated, for example, for stannic chloride acetylation of methyl and r-butyl derivatives of benzene and thiophene. Partial rate factors, relative to the unsubstituted aromatic, are shown in Scheme 6.1 (71T4667). 

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