Alkyl halides, from alcohols nomenclature

Section 4.2 Alcohols and alkyl halides may be named using either substitutive or functional class lUPAC nomenclature. In substitutive nomenclature alkyl halides are named as halogen derivatives of alkanes. The parent is the longest continuous chain that bears the halogen substituent, and in the absence of other substituents the chain is numbered from the direction that gives the lower number to the carbon that... 

At about the same time, Alexander W. Williamson (England 1824-1904) showed how ethers ethers contain the C-O-C linkage) could be prepared from the potassium salt of an alcohol (an alcohol contains a C-O-H unit). The potassium salt is the conjugate base of that alcohol, C-0 K+, and the oxygen atom of that species reacts with an alkyl halide, which contains a C-X bond. In this representation, X is a halogen and alkyl is the term used for a unit containing carbons and hydrogen atoms. The nomenclature for all of these compounds will be described in Chapters 3 and 4. 

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