Search results
Results From The WOW.Com Content Network
The reaction has been shown to work in aromatic, semi-aromatic, aliphatic, and heterocyclic substrates. The reaction works best when the ketone functional groups have no adjacent enolizable protons, as this allows aldol condensation to compete. The reaction is formally a ring contraction when used on cyclic diketones.
Benzyl is not to be confused with phenyl with the formula C 6 H 5. The term benzylic is used to describe the position of the first carbon bonded to a benzene or other aromatic ring. For example, (C 6 H 5)(CH 3) 2 C + is referred to as a "benzylic" carbocation. The benzyl free radical has the formula C 6 H 5 CH 2 •.
The Wohl–Ziegler reaction [1] [2] is a chemical reaction that involves the allylic or benzylic bromination of hydrocarbons using an N-bromosuccinimide and a radical initiator. [3] Best yields are achieved with N-bromosuccinimide in carbon tetrachloride solvent. Several reviews have been published. [4] [5]
In organic chemistry, neighbouring group participation (NGP, also known as anchimeric assistance) has been defined by the International Union of Pure and Applied Chemistry (IUPAC) as the interaction of a reaction centre with a lone pair of electrons in an atom or the electrons present in a sigma or pi bond contained within the parent molecule but not conjugated with the reaction centre.
For example, the amino acid tyrosine could be protected as a benzyl ester on the carboxyl group, a fluorenylmethylenoxy carbamate on the amine group, and a tert-butyl ether on the phenol group. The benzyl ester can be removed by hydrogenolysis, the fluorenylmethylenoxy group (Fmoc) by bases (such as piperidine), and the phenolic tert -butyl ...
These cause a downfield shift of approximately 2–4 ppm for H atoms on C α (an aliphatic C atom directly bonded to the substituent in question) and of less than 1–2 ppm for H atoms on C β (an aliphatic C atom bonded to C α). Carbonyl groups, olefinic fragments and aromatic rings contribute sp 2 hybridized
This can also explain why phosphorus in phosphanes can't donate electron density to carbon through induction (i.e. +I effect) although it is less electronegative than carbon (2.19 vs 2.55, see electronegativity list) and why hydroiodic acid (pKa = -10) being much more acidic than hydrofluoric acid (pKa = 3).
As is typical for an S N 2 process, benzylic, allylic, and α-carbonylated alkyl halides are excellent reactants. Even though alkyl chlorides are poor alkylating agents ( gem -dichlorides especially so), amines should not be handled in chlorinated solvents such as dichloromethane and dichloroethane, especially at high temperatures, due to the ...