Chemistry-
General
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Question

Karl Ziegler reported that alkenes react with N-bromosuccinimide (NBS) in presence of light to give products resulting from substitution of hydrogen by bromjne at the allylic position, i.e., the position next to the double bond. Let us consider the halogenation of cyclohexene.

Energy level diagram for allylic, vinylic and alkylic, free radicals is .given below:

In the treatment of cyclohexene with NBS, which of the following products will be least stable?

  1.    
  2.    
  3.    
  4. Cannot be predicted    

The correct answer is:

Related Questions to study

General
Chemistry-

The high reactivity of alkyl halides can be explained in terms of nature of C-X bond which is highly polarised covalent bond due to large difference in the electronegativities of carbon and halogen .atom. This polarity is responsible for the nucleophilic substitution reactions of alky- halides which mostly occur by S subscript N to the power of 1 end exponent end subscript and S subscript N to the power of 2 end exponent end subscript mechanisms S subscript N to the power of 1 end exponent end subscript reaction is a two step process . and in the first step, R-X ionises to give carbocation (slow process). In the second step, the nucleophile attacks the carbocation from either side to form the product (fast process). In S subscript N to the power of 1 end exponent end subscript reaction, there can be racemization and inversion. S subscript N to the power of 1 end exponent end subscript reaction is favoured by heavy (bulky) groups on the carbon atom attached to halogens. i.e., R subscript 3 end subscript C minus X greater than R subscript 2 end subscript C H minus X greater than R minus C H subscript 2 end subscript X greater than C H subscript 3 end subscript X
In S subscript N to the power of 2 end exponent end subscript reaction, the strong nucleophile OH- attacks from the opposite side of the chlorine atom to give an intermediate (transition state). which breaks to yield the product (alcohol) and leavj.ng open parentheses X to the power of minus end exponent close parentheses group. The alcohol has a configuration opposite to drat 'of the bromide and is said to proceed with inversion of configuration. S subscript N to the power of 2 end exponent end subscript reaction is favoured by small groups on the carbon atom attached to halogen i.e., C H subscript 3 end subscript minus X greater than R minus C H subscript 2 end subscript X greater than R subscript 2 end subscript C H X greater than R subscript 3 end subscript C minus X
The main product formed in the following reaction is:

The high reactivity of alkyl halides can be explained in terms of nature of C-X bond which is highly polarised covalent bond due to large difference in the electronegativities of carbon and halogen .atom. This polarity is responsible for the nucleophilic substitution reactions of alky- halides which mostly occur by S subscript N to the power of 1 end exponent end subscript and S subscript N to the power of 2 end exponent end subscript mechanisms S subscript N to the power of 1 end exponent end subscript reaction is a two step process . and in the first step, R-X ionises to give carbocation (slow process). In the second step, the nucleophile attacks the carbocation from either side to form the product (fast process). In S subscript N to the power of 1 end exponent end subscript reaction, there can be racemization and inversion. S subscript N to the power of 1 end exponent end subscript reaction is favoured by heavy (bulky) groups on the carbon atom attached to halogens. i.e., R subscript 3 end subscript C minus X greater than R subscript 2 end subscript C H minus X greater than R minus C H subscript 2 end subscript X greater than C H subscript 3 end subscript X
In S subscript N to the power of 2 end exponent end subscript reaction, the strong nucleophile OH- attacks from the opposite side of the chlorine atom to give an intermediate (transition state). which breaks to yield the product (alcohol) and leavj.ng open parentheses X to the power of minus end exponent close parentheses group. The alcohol has a configuration opposite to drat 'of the bromide and is said to proceed with inversion of configuration. S subscript N to the power of 2 end exponent end subscript reaction is favoured by small groups on the carbon atom attached to halogen i.e., C H subscript 3 end subscript minus X greater than R minus C H subscript 2 end subscript X greater than R subscript 2 end subscript C H X greater than R subscript 3 end subscript C minus X
The main product formed in the following reaction is:

Chemistry-General
General
Chemistry-

Compound  undergoes intramolecular nucleophilic substitution of the type .... giving .

Compound  undergoes intramolecular nucleophilic substitution of the type .... giving .

Chemistry-General
General
Chemistry-

In the following compounds, nucleophile and the leaving groups are in the same molecule:
I) 
II) 
III) 
IV) 
These dual nature species can undergo intramolecular and intermolecular nucleophilic substitution. Intramolecular substitution reaction is possible in:

In the following compounds, nucleophile and the leaving groups are in the same molecule:
I) 
II) 
III) 
IV) 
These dual nature species can undergo intramolecular and intermolecular nucleophilic substitution. Intramolecular substitution reaction is possible in:

Chemistry-General
parallel
General
Chemistry-

Ullmann reaction is given by:

Ullmann reaction is given by:

Chemistry-General
General
Chemistry-

The major product of the reaction,
 with HBr is:

The major product of the reaction,
 with HBr is:

Chemistry-General
General
Chemistry-

The reaction given
 is:

The reaction given
 is:

Chemistry-General
parallel
General
Chemistry-

In the reaction,

the compound (C) is:

In the reaction,

the compound (C) is:

Chemistry-General
General
Chemistry-

The major product obtained in the reaction,

The major product obtained in the reaction,

Chemistry-General
General
Chemistry-

In which of the following reactions, an optically. active single product is formed?

In which of the following reactions, an optically. active single product is formed?

Chemistry-General
parallel
General
Chemistry-

When  reacts with KOH in presence of water (through S subscript N to the power of 2 end exponent end subscript reaction mechanism) then stereochemistry of product so formed will be:

When  reacts with KOH in presence of water (through S subscript N to the power of 2 end exponent end subscript reaction mechanism) then stereochemistry of product so formed will be:

Chemistry-General
General
Chemistry-

Which of the following is ,fast de-brominated?

Which of the following is ,fast de-brominated?

Chemistry-General
General
Maths-

If a, b, c are lengths of the sides of a triangle, then open parentheses a plus b plus c close parentheses to the power of 3 end exponent is

If a, b, c are lengths of the sides of a triangle, then open parentheses a plus b plus c close parentheses to the power of 3 end exponent is

Maths-General
parallel
General
Maths-

If a, b, c are +ve, then a to the power of 2 end exponent plus b to the power of 2 end exponent plus c to the power of 2 end exponent is

If a, b, c are +ve, then a to the power of 2 end exponent plus b to the power of 2 end exponent plus c to the power of 2 end exponent is

Maths-General
General
Maths-

3 distinct integers are selected at random from 1, 2, 3,…, 20. The probability that the sum is divisible by 5 is

3 distinct integers are selected at random from 1, 2, 3,…, 20. The probability that the sum is divisible by 5 is

Maths-General
General
Maths-

If open vertical bar table row a b 0 row 0 a b row b 0 a end table close vertical bar equals 0 , then

If open vertical bar table row a b 0 row 0 a b row b 0 a end table close vertical bar equals 0 , then

Maths-General
parallel

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