Bensüülrühm

The benzyl group, often abbreviated as Bn, is a functional group in organic chemistry with the formula C6H5CH2-. It is a phenyl group (C6H5-) attached to a methylene group (-CH2-). The benzyl group is derived from toluene (methylbenzene) by removal of one hydrogen atom from the methyl group.

In chemical nomenclature, the term "benzyl" refers specifically to the C6H5CH2- group. For instance, benzyl alcohol is C6H5CH2OH, and benzyl chloride is C6H5CH2Cl. The benzyl group is an aromatic substituent.

One of the key properties of the benzyl group is its relative stability, particularly compared to other alkyl groups. The phenyl ring delocalizes the electron density, contributing to the stability of carbocations, radicals, and carbanions at the benzylic position. This stability makes the benzyl group a useful protecting group in organic synthesis. For example, benzyl ethers are often used to protect alcohols, as they can be selectively cleaved under mild conditions, typically by hydrogenolysis.

The benzylic position is also susceptible to certain chemical reactions. For instance, benzylic hydrogens are relatively acidic and can be removed by strong bases to form benzylic carbanions. Furthermore, benzylic positions are prone to oxidation. The presence of the benzyl group can significantly influence the reactivity and properties of a molecule.