The haloalkanes include saturated aliphatic compounds, in the molecules of which there is a halogen atom instead of one or more hydrogen atoms. In the class of haloalkanes, isomerism of the structure of the carbon skeleton is observed, such as normal and branched chains. This is due to the different arrangement of the halogen in the molecule, and optical isomerism, for example, in R- and S-2-chlorobutane. Official nomenclature (IUPAC) names are formed by choosing the longest unbranched chain and numbered to indicate the positions of the substituents (Ouellette & Rawn, 2018). Halogenated alkanes are classified according to the type of carbon atom at which halogen stands, into primary, secondary, and tertiary.
Processes for the preparation of organic halides can be combined into two groups, such as substitution reactions and addition reactions. The choice of the path and reaction conditions depend on the structure of the carbon skeleton of the halogenated molecule and the atom or group of units that are being replaced (Ouellette & Rawn, 2018). Hydrogen in alkanes and alkyl groups bound to the alkenyl or aryl moiety is replaced by the action of a halogen under illumination or heating. In other words, all this happens under the conditions of a free radical reaction.
During one-step SN2 process the substrate is attacked by a nucleophile, and the overall rate of the reactions are interdependent on each other. The collision chance is also reliant on the concentration of substrate or both elements. Due to having a single stage, the occurrence can be described as concerted. It can be illustrated through SN2 reaction of chloromethane and hydroxide ion, where the bond carbon and the ion with adjacent one breaking at the same rate.
Reference
Ouellette, R. J., & Rawn, J. D. (2018). Haloalkanes and alcohols nucleophilic substitution and elimination reactions. Organic Chemistry, 255–298.