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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.
Alkyl halides differ greatly in the ease with which they undergo the Finkelstein reaction. The reaction works well for primary (except for neopentyl) halides, and exceptionally well for allyl, benzyl, and α-carbonyl halides. Secondary halides are far less reactive.
In this method, the sodium or potassium salt of phthalimide is N-alkylated with a primary alkyl halide to give the corresponding N-alkylphthalimide. [8] [9] [10] Upon workup by acidic hydrolysis the primary amine is liberated as the amine salt. [11] Alternatively the workup may be via the Ing–Manske procedure, involving reaction with hydrazine.
Primary alkyl halides undergo reduction to the corresponding alkanes in the presence of NaAlH(OH)(OCH 2 CH 2 OCH 3) 2. Secondary halides are less reactive, but afford alkanes in reasonable yield. Secondary halides are less reactive, but afford alkanes in reasonable yield.
In the case of primary alkyl halides, the carbocation-like complex (R (+)---X---Al (-) Cl 3) will undergo a carbocation rearrangement reaction to give almost exclusively the rearranged product derived from a secondary or tertiary carbocation. [8] Protonation of alkenes generates carbocations, the electrophiles.
A graph showing the relative reactivities of the different alkyl halides towards S N 1 and S N 2 reactions (also see Table 1). In 1935, Edward D. Hughes and Sir Christopher Ingold studied nucleophilic substitution reactions of alkyl halides and related compounds. They proposed that there were two main mechanisms at work, both of them competing ...
In the Williamson ether reaction there is an alkoxide ion (RO −) which acts as the nucleophile, attacking the electrophilic carbon with the leaving group, which in most cases is an alkyl tosylate or an alkyl halide. The leaving site must be a primary carbon, because secondary and tertiary leaving sites generally prefer to proceed as an ...
For example, 1-bromo-1-fluoroethane can undergo nucleophilic attack to form 1-fluoroethan-1-ol, with the nucleophile being an HO − group. In this case, if the reactant is levorotatory, then the product would be dextrorotatory, and vice versa. [3] S N 2 mechanism of 1-bromo-1-fluoroethane with one of the carbon atoms being a chiral centre.