Reaction intermediate

The IUPAC Gold Book defines[3] an intermediate as a compound that has a lifetime greater than a molecular vibration, is formed (directly or indirectly) from the reactants, and reacts further to give (either directly or indirectly) the products of a chemical reaction.

[4] A carbanion is an organic molecule where a carbon atom is not electron deficient but contain an overall negative charge.

Carbanions are strong nucleophiles, which can be used to extend an alkene's carbon backbone in the synthesis reaction shown below.

[4] Radicals are highly reactive and short-lived, as they have an unpaired electron which makes them extremely unstable.

The formed product, a carbon radical, can react with non-radical molecule to continue propagation or react with another radical to form a new stable molecule such as a longer carbon chain or an alkyl halide.

Initiation: This reaction can occur by thermolysis (heating) or photolysis (absorption of light) leading to the breakage of a molecular chlorine bond.

During the propagation of the reaction, there are several highly reactive species that will be removed and stabilized at the termination step.

Termination: This kind of reaction takes place when the radical species interact directly.

The products of the termination reactions are typically very low yield in comparison to the main products or intermediates as the highly reactive radical species are in relatively low concentration in relation to the rest of the mixture.

There are many different termination combinations, some examples are: Union of methyl radicals from a C-C bond leading to ethane (a side product).

An example of this is demonstrated with the enzyme reaction intermediate of metallo-β-lactamase, which bacteria can use to acquire resistance to commonly used antibiotics such as penicillin.

Spectroscopy techniques have found that the reaction intermediate of metallo-β-lactamase uses zinc in the resistance pathway.

[6] Another example of the importance of reaction intermediates is seen with AAA-ATPase p97, a protein that used in a variety of cellular metabolic processes.

[7] An additional example of biologically relevant reaction intermediates can be found with the RCL enzymes, which catalyzes glycosidic bonds.