1 Complete the following table by filing in the boses with the appropriate starting material, rengent or product 1. NANH, NH, 2 EIBr LUndars catalyst 1. BH-THF 2. NICH, HO NaGH DMSO 2 equivalence HBr
Reactive Intermediates
In chemistry, reactive intermediates are termed as short-lived, highly reactive atoms with high energy. They rapidly transform into stable particles during a chemical reaction. In specific cases, by means of matrix isolation and at low-temperature reactive intermediates can be isolated.
Hydride Shift
A hydride shift is a rearrangement of a hydrogen atom in a carbocation that occurs to make the molecule more stable. In organic chemistry, rearrangement of the carbocation is very easily seen. This rearrangement can be because of the movement of a carbocation to attain stability in the compound. Such structural reorganization movement is called a shift within molecules. After the shifting of carbocation over the different carbon then they form structural isomers of the previous existing molecule.
Vinylic Carbocation
A carbocation where the positive charge is on the alkene carbon is known as the vinyl carbocation or vinyl cation. The empirical formula for vinyl cation is C2H3+. In the vinyl carbocation, the positive charge is on the carbon atom with the double bond therefore it is sp hybridized. It is known to be a part of various reactions, for example, electrophilic addition of alkynes and solvolysis as well. It plays the role of a reactive intermediate in these reactions.
Cycloheptatrienyl Cation
It is an aromatic carbocation having a general formula, [C7 H7]+. It is also known as the aromatic tropylium ion. Its name is derived from the molecule tropine, which is a seven membered carbon atom ring. Cycloheptatriene or tropylidene was first synthesized from tropine.
Stability of Vinyl Carbocation
Carbocations are positively charged carbon atoms. It is also known as a carbonium ion.
The reaction of an alkyne with sodium amide leads to the formation of a carbanion by removal of acidic hydrogen from alkyne which further on reaction with EtBr forms a substituted product by reaction with the electrophile Et as follows:
The reaction of an alkene with a halogen leads to the formation of vicinal dihalide which further on reaction with sodium amide produces an alkyne. Thus, the complete reaction would be represented as follows:
The work of Lindlar’s catalyst is to form a cis-alkene. The cis-alkene so formed reacts with boron hydride in the presence of THF to form an alcohol following anti markovnikov rule. Thus, the reaction is represented as follows:
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