A species having a carbon atom possessing a sextet (6 in a group) of electrons and a positive charge is called a carbocation (earlier called carbonium ion). The +CH3 ion is known as a methyl cation or methyl carbonium ion. Carbocations are classified as primary, secondary or tertiary depending on whether one, two or three carbons are directly attached to the positively charged carbon. Carbocations are highly unstable and reactive species. Alkyl groups directly attached to the positively charged carbon stabilise the carbocations due to inductive and hyperconjugation effects. The observed order of carbocation stability is: +CH3 < CH3C+H2 < (CH3)2C+H < (CH3)3C+. These carbocations have a trigonal planar shape with positively charged carbon being sp2 hybridised. Thus, the shape of +CH3 may be considered as being derived from the overlap of three equivalent C(sp2) hybridised orbitals with 1s orbital of each of the three hydrogen atoms. Each bond may be represented as C(sp2)–H(1s) sigma bond. The remaining carbon orbital is perpendicular to the molecular plane and contains no electrons. The shape of methyl carbocation is given as below:
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JEE MAIN | Some Basic Principles of Organic Chemistry |
The shape of carbocation is
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The total number of optically active compounds formed in the following reaction is :
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The order of stability of the following carbocations:
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The general order for stability or carbocations is
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Which of the following carbocation is more stable ?
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Arrange the following carbocations in decreasing order of stability
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Which of the following carbocations is most stable?
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Among the given species the Resonance stabilised carbocations are:
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The correct order of stability of given carbocation is:
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The acidic hydrolysis of ether [x] shown below is fastest when :
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Which of the following contains 3 pairs of electron in the valence shell ?
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Which of the following carbocation has maximum ease of formation ?
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Which of the following is the most stable carbocation ?
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Predict the major product in the following reaction :
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The major product (A) formed in the reaction
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The major product in the following reaction is :
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The most stable carbocation for the following is:
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The decreasing order of hydride affinity for following carbonations is:
The decreasing order of hydride affinity for following carbonations is:
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The correct stability order of carbocations is
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A species having a carbon atom possessing sextext of electrons and a positive charge is called a carbocation