Alkyl halides Compounds with halogen elimination reaction

In this and the next chapter, we ll be discussing the chemistry of alkyl halides—compounds that have a halogen atom bonded to a saturated, s/> -hybridized carbon atom. We ll begin in this chapter with a look at how to name and prepare alkyl halides, and we ll see several of their reactions. Then in the following chapter, we ll make a detailed study of the substitution and elimination reactions of alkyl halides—two of the most important and well-studied reaction types in organic chemistry. 

The polarity of carbon-halogen bond of alkyl halides is responsible for their nucleophilic substitution, elimination and their reaction with metal atoms to form organometallic compounds. Nucleophilic substitution reactions are categorised into and on the basis of their kinetic properties. Chirality has a profound role in understanding the reaction mechanisms of Sj l and Sj 2 reactions. Sj 2 reactions of chiral all l halides are characterised by the inversion of configuration while Sj l reactions are characterised by racemisation. 

In most cases, bromo or chloro derivatives are used as starting materials. The 1,2-dihaloalkanes are usually prepared from the alkenes by halogen addition, the 1,1-dihaloalkanes from the corresponding carbonyl compounds with PCI5 or other acid chlorides (Scheme 31). Some 1,1-dichloroalkanes can be prepared from vinyl chloride by addition of a secondary or tertiary alkyl chloride (Scheme 32). The 1-haloalkenes can be prepared from either the 1,2- or the 1,1-dihaloalkanes by elimination of 1 mol of hydrogen halide or by a Wittig reaction (Scheme 33). 

Several papers report on the nucleophilic reactivity of dithiocarbamate ions towards alkyl halides, 1,2-dibromoalkyl compounds, alkyl and aryl chloroformates, chloroacetic acid, chloroacetates, 3-halo-genophthalides, sulphenyl chlorides, sultones, and trialkylam-monium compounds. Examples of a similar reactivity of dithiocarbazate anions have also appeared. " A series of papers deal with addition or addition-elimination reactions of dithiocarbamate - or dithiocarbazate anions with w-nitrostyrene, 2-thioxo-, 2-oxo-, and 2-imino-5-methoxycarbonylmethylidene-4-thiazolidones, dimethyl acetylenedicar-boxylate, and NN -dialkyl phenylpropiolamidines. S-Monoalkylated N-cyanodithioimidocarbonates (492) underwent oxidative ring-closure to give 3-halogeno-l,2,4-thiadiazole sulphides (493) on treatment with halogenating agents. ... 

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