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PhF behaves rather differently from other halobenzene derivatives owing to the pi-donor properties of fluoride. For example, the para position is more activated than benzene toward electrophiles. For this reason, it can be converted to 1-bromo-4-fluorobenzene with relatively high efficiency. [3]
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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.
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In organic chemistry, an electrophilic aromatic halogenation is a type of electrophilic aromatic substitution.This organic reaction is typical of aromatic compounds and a very useful method for adding substituents to an aromatic system.
The following is the reaction mechanism of a nucleophilic aromatic substitution of 2,4-dinitrochlorobenzene (1) in a basic solution in water. Nucleophilic aromatic substitution Since the nitro group is an activator toward nucleophilic substitution, and a meta director, it is able to stabilize the additional electron density (via resonance) when ...
Aside from these effects, there is often also a steric effect, due to increased steric hindrance at the ortho position but not the para position, leading to a larger amount of the para product. The effect is illustrated for electrophilic aromatic substitutions with alkyl substituents of differing steric demand for electrophilic aromatic nitration.
For example, 2,4-dinitrochlorobenzene reacts in basic solution to give a phenol. Unlike in most other substitution reactions, fluoride is the best leaving group, and iodide the worst. [ 16 ] A 2018 paper indicates that this situation may actually be rather common, occurring in systems that were previously assumed to proceed via S N Ar mechanisms.