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The bimolecular nucleophilic substitution (S N 2) is a type of reaction mechanism that is common in organic chemistry. In the S N 2 reaction, a strong nucleophile forms a new bond to an sp 3 -hybridised carbon atom via a backside attack, all while the leaving group detaches from the reaction center in a concerted (i.e. simultaneous) fashion.
There are many reactions in organic chemistry involving this type of mechanism. Common examples include: Organic reductions with hydrides, for example; R−X → R−H using LiAlH 4 (S N 2) Hydrolysis reactions such as; R−Br + OH − → R−OH + Br − (S N 2) or R−Br + H 2 O → R−OH + HBr (S N 1) Williamson ether synthesis
Coupling reactions are a class of metal-catalyzed reactions involving an organometallic compound RM and an organic halide R′X that together react to form a compound of the type R-R′ with formation of a new carbon–carbon bond. Examples include the Heck reaction, Ullmann reaction, and Wurtz–Fittig reaction. Many variations exist. [3]
An example of a simple chain reaction is the thermal decomposition of acetaldehyde (CH 3 CHO) to methane (CH 4) and carbon monoxide (CO). The experimental reaction order is 3/2, [4] which can be explained by a Rice-Herzfeld mechanism. [5] This reaction mechanism for acetaldehyde has 4 steps with rate equations for each step :
Molecularity, on the other hand, is deduced from the mechanism of an elementary reaction, and is used only in context of an elementary reaction. It is the number of molecules taking part in this reaction. This difference can be illustrated on the reaction between nitric oxide and hydrogen: [11]
An example of a reaction taking place with an S N 1 reaction mechanism is the hydrolysis of tert-butyl bromide forming tert-butanol: This S N 1 reaction takes place in three steps: Formation of a tert -butyl carbocation by separation of a leaving group (a bromide anion) from the carbon atom: this step is slow.
Another example is the unimolecular nucleophilic substitution (S N 1) reaction in organic chemistry, where it is the first, rate-determining step that is unimolecular. A specific case is the basic hydrolysis of tert-butyl bromide (t-C 4 H 9 Br) by aqueous sodium hydroxide. The mechanism has two steps (where R denotes the tert-butyl radical t-C ...
Nuclear chemistry is a sub-discipline of chemistry that involves the chemical reactions of unstable and radioactive elements where both electronic and nuclear changes can occur. The substance (or substances) initially involved in a chemical reaction are called reactants or reagents.