Which of the following is in conjugation ?
CH2=CH−⊖CH2
CH2=CH−CH=CH−⊕CH2
CH2=CH−..NH2
CH2=CH−CH=CH−⊕CH2
Know about the conjugate systems Recall the types of conjugates we can have.
Alternate positions of the molecule having π bond, positive charge, negative charge, odd electron or lone paif of electrons are known as conjugative positions.
Note: Compound having at least two conjugate positions is known as conjugated compound.
Type of conjugates
(i) π,πconjugation: If all conjugate positions have π bonds, then conjugation is known as π,πconjugation
CH21=CH−C3H=CH2
C1H3−CH−2−CH1−CH=CH−CH5=CH2
All of the above compounds have π,πconjugation.
(ii) Positive charge, π Conjugation: In this case all conjugate positions have π bonds and only one conjugate position has positive charge. If this is the case, then conjugation is known as positive charge, π conjugation
H12=CH−⊕CH32
It has positive charge, π conjugation.
This species has two type of conjugation π,πconjugation and positive charge,πconjugation
(iii) Negative charge,πconjugation: If all conjugate positions have π bonds and only one conjugate position has negative charge, then conjugation is known as negative charge, πconjugation
CH2=CH−⊖CH2
CH2=CH−CH−CH=CH−⊖CH2
(iv) Odd electron, πconjugation: If all conjugate positions have π bonds and one conjugate position has odd electron, then conjugation is known as odd electron, πconjugation.
(v) Lone pair, πconjugation: if all conjugate positions have π bonds and only one conjugate position has lp then conjugation is known as lp, πconjugation.
CH2=CH−..NH2 CH2 = CH−..X..:
CH21=CH−CH2=CH−CH5 − ..N7H2
Therefore, all A,B,C And D are correct.