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In primary (1°) haloalkanes, the carbon that carries the halogen atom is only attached to one other alkyl group. An example is chloroethane (CH 3 CH 2 Cl). In secondary (2°) haloalkanes, the carbon that carries the halogen atom has two C–C bonds. In tertiary (3°) haloalkanes, the carbon that carries the halogen atom has three C–C bonds.
The reaction involves a carbocation intermediate and is commonly seen in reactions of secondary or tertiary alkyl halides under strongly basic conditions or, under strongly acidic conditions, with secondary or tertiary alcohols. With primary and secondary alkyl halides, the alternative S N 2 reaction occurs.
In addition, each position on an alkyl chain can be described according to how many other carbon atoms are attached to it. The terms primary, secondary, tertiary, and quaternary refer to a carbon attached to one, two, three, or four other carbons respectively.
Experiments have shown that all halogenation produces a mixture of all possible isomers, indicating that all hydrogen atoms are susceptible to reaction. The mixture produced, however, is not statistical: Secondary and tertiary hydrogen atoms are preferentially replaced due to the greater stability of secondary and tertiary free-radicals.
The experimental relative chlorination rates at primary, secondary, and tertiary positions match the corresponding radical species' stability: tertiary (5) > secondary (3.8) > primary (1). Thus any single chlorination step slightly favors substitution at the carbon already most substituted.
The alkoxide (or aryloxide) may be primary and secondary. Tertiary alkoxides tend to give elimination reaction because of steric hindrance. The alkylating agent, on the other hand is most preferably primary. Secondary alkylating agents also react, but tertiary ones are usually too prone to side reactions to be of practical use.
Simple primary, secondary and tertiary sp 3 carbanions (e.g., ethanide CH 3 CH − 2, isopropanide (CH 3) 2 CH −, and t-butanide (CH 3) 3 C − were subsequently determined to be unbound species (the EAs of CH 3 CH 2 •, (CH 3) 2 CH•, (CH 3) 3 C• are −6, −7.4, −3.6 kcal/mol, respectively) indicating that α substitution is ...
Secondary is a term used in organic chemistry to classify various types of compounds (e. g. alcohols, alkyl halides, amines) or reactive intermediates (e. g. alkyl radicals, carbocations). An atom is considered secondary if it has two 'R' Groups attached to it. [ 1 ]