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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]
N-Bromosuccinimide or NBS is a chemical reagent used in radical substitution, electrophilic addition, and electrophilic substitution reactions in organic chemistry. NBS can be a convenient source of Br • , the bromine radical.
Several reagents can be substituted for bromine. Sodium hypochlorite, [4] lead tetraacetate, [5] N-bromosuccinimide, and (bis(trifluoroacetoxy)iodo)benzene [6] can effect a Hofmann rearrangement. The intermediate isocyanate can be trapped with various nucleophiles to form stable carbamates or other products rather than undergoing decarboxylation.
Bromine itself can be used, but due to its toxicity and volatility, safer brominating reagents are normally used, such as N-bromosuccinimide. The principal reactions for organobromides include dehydrobromination, Grignard reactions, reductive coupling, and nucleophilic substitution. [15]
Free-radical reactions depend on one or more relatively weak bonds in a reagent. Under reaction conditions (typically heat or light), some weak bonds homolyse into radicals, which then induce further decomposition in their compatriots before recombination. Different mechanisms typically apply to reagents without such a weak bond.
Structure of N-bromosuccinimide, a common brominating reagent in organic chemistry. Like the other carbon–halogen bonds, the C–Br bond is a common functional group that forms part of core organic chemistry. Formally, compounds with this functional group may be considered organic derivatives of the bromide anion.
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 :
Reagents are "substances or compounds that are added to a system in order to bring about a chemical reaction or are added to see if a reaction occurs." [1] Some reagents are just a single element. However, most processes require reagents made of chemical compounds. Some of the most common ones used widely for specific reactive functions are ...