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Assertion (A) The compound tetraene has ...

Assertion (A) The compound tetraene has the following structural formul.

It is cyclic and has conjugated `8pi`-electron system but it is not an aromatic compound.
Reason (R ) `(4n + 2)pi` electrons rule does not hold good and ring is not planar.

A

Both A and B are correct and R is the correct explanation of A

B

Both A and R are not correct

C

Both A and R are not correct

D

A is not correct but R is correct

Text Solution

Verified by Experts

The correct Answer is:
a
Both assertion and reason are correct and reason is the correct explanation of assertion .
According to Huckel rule Aromaticity is shown by compounds possessing following characteristics
(i) compound must be planar and cycilc
(ii) Complete delocalisation of `pi` electrons in the ring
(iii) Presence of conjugated `(4n+2) pi` electrons in the ring where n is an integer (n=0, 1, 2,...) cyclo octatetraeng (given ) has a tub like structure . It loses planaritt\y. No. of `pie^(-)` delocalised = 8 and n is not integer. Hence, cyclotatetraene is a non-aromatic compound.
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Knowledge Check

  • This section contains Assertion (A) and Reason® type questions each question has choices (1)(2)(3)(4) out of which only one is correct Assertion: The compound cyclooctane has the following structural formula it is cyclic and has conjugated 8pi electron system but it is not an aromatic compound Reason: (4n+2)pi electrons rule does not hold good and ring is not planar

    A
    Both A and R are correct ,R is the correct explanation of A
    B
    Both A and R are correct,R is not the correct explanation of A
    C
    A is correct ,R is incorrect
    D
    R is correct,A is incorrect

  • A compound, PQ_2 has the following arrangement of electrons : The elements P and Q are respectively:

    A
    N,Cl
    B
    Cl,S
    C
    O,F
    D
    Na,F

  • Assertion : Pyrrole is an aromatic heterocyclic compound . Reason:It has a cyclic , delocalised 6pi electrons

    A
    If both assertion and reason are true and the reason is the correct explanation of the assertion
    B
    If both assertion and reason are true but reason is not the correct explanation of the assertion
    C
    if assertion is true but reason is false
    D
    If assertion and reason both are false

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    The number of pi electrons required for a planar cyclic conjugated system to exhibit aromatic behaviour is (4n+2) . Here n is

    Assertion (A) : Thhe compound called inorganic benzene s borazine. Reason (R) : Borazine has a structure similar to benzene.

    Assertion (A) : SeCl_4 does not have a tetrahedral structure. Reason (R) :Se in SeCl_4 has two lone pairs.

    We have now learned that benzene is unsually stable, and that this stability seems to be correlated with the overlap of its carbon 2p orbitals to form pi molecular orbitals. In 1931. Erich Huckel (1896 - 1980), a German chemist physicist, elucidated with molecular orbital arguments the criteria for this sort of stability, which has come to be called aromaticity. Criteria for aromaticity : * Aromatic compounds contain one or more rings that have a cyclic arragement of p-orbitals. Thus, aromaticity is a property of certain cyclic compounds. * Every atom of an aromatic ring has a p-orbital. * Aromatic rings are planar. The cyclic arrangements of p-orbitals in an aromatic compound must contain 4n+2pi electrons, where n is any positive integer (0, 1, 2, ....). In other words, an aromatic ring must contain 2, 6, 10 pi electrons. Which of the following compound is not anti-aromatic ?

    We have now learned that benzene is unsually stable, and that this stability seems to be correlated with the overlap of its carbon 2p orbitals to form pi molecular orbitals. In 1931. Erich Huckel (1896 - 1980), a German chemist physicist, elucidated with molecular orbital arguments the criteria for this sort of stability, which has come to be called aromaticity. Criteria for aromaticity : * Aromatic compounds contain one or more rings that have a cyclic arragement of p-orbitals. Thus, aromaticity is a property of certain cyclic compounds. * Every atom of an aromatic ring has a p-orbital. * Aromatic rings are planar. The cyclic arrangements of p-orbitals in an aromatic compound must contain 4n+2pi electrons, where n is any positive integer (0, 1, 2, ....). In other words, an aromatic ring must contain 2, 6, 10 pi electrons. Which of the following compound is non-aromatic ?

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