This chapter involves compounds of various classes that have the following functional groups: halogens, -OH, -O-, -SH, -S-, and -NH2. General formulas of the classes are given below, where R is aliphatic or aromatic radical (except for alcohols and phenols):
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It is easy to see that all the functional groups are attached to a carbon framework by a single bond which is polar to a greater or a lesser extent. This provides some common chemical properties of the mentioned classes though they have substantial distinctions.
Compounds containing the amino and hydroxyl groups are of very common occurrence in nature. Organic halides, on the contrary, are rarely encountered in higher plants and animals. Most of them are creations of the laboratory chemists. They are employed as industrial solvents, refrigerants, pesticides in agriculture, inhaled anesthetics in medicine and so on. Moreover, organic halides are versatile reagents in syntheses since they can be converted into many other classes of organic compounds, including the objects of this chapter. We begin the consideration with organic halogen compounds.
7.1. ORGANIC HALIDES
Organic halides are hydrocarbon derivatives in which one or more halogen at&hide_Cookie=yes)
oms replace hydrogen atom(s).
In this section the main attention will be paid to alkyl halides in which a halogen is attached to saturated, sp3-hybridized carbon. Other types of organic halides, such as aryl halides and vinyl halides, RCH=CHHal, also exist. Halogen in these compounds is bonded to sp2-hybridized carbon, therefore they differ greatly in their chemistry from alkyl halides.
Before discussing the chemistry of alkyl halides, let us consider reactive sites in a structure of the saturated compound of the general formula R-X, where X is an electron-withdrawing group. Polarization of a C-X bond results in the formation of an electrophilic site (the α carbon) that can be attacked by a nucleophilic reagent. The