The Nomenclature of Disubstituted and Polysubstituted Benzenes

Show how the following conqtounds could be prepared from benzene  

Solution to 10a Benzaldehyde can be prepared by the Gatterman-Koch reaction (page 919) or by the following sequence of reactions  

Section 19.1 described how monosubstituted benzenes are named. Now we will look at how benzene rings that have more than one substituent are named. 

The relative positions of two substituents on a benzene ring can be indicated either by numbers or by the prefixes ortho, meta, and para. Adjacent substituents are called ortho, substituents separated by one carbon are called meta, and substituents located opposite one another are called para. Often, the abbreviations for these prefixes (0, m, p) are used in compounds names. 

If the two substituents are different, they are listed in alphabetical order, each preceded by it assigned number. The first mentioned substituent is given the 1-position, and the ring is numbered in the direction that gives the second substituent the lowest possible number. 

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