285325
Among the following:
I
II
III
IV
V
The set which represents aromatic species is
1 I, II and III
2 III, IV and IV
3 II and III
4 I, II and IV
Explanation:
(d) Aromatic species :- ( \(4 \mathrm{n}+2 \pi\) electrons)I
II
Anti-aromatic : - ( \(4 \mathrm{n} \pi\) electrons)
III
V
Karnataka CET 2023
CHEMISTRY(KCET)
285328
Arrange benzene,\(n\)-hexane and ethyne in decreasing order of their acidic behaviour.
1 Benzene\(>n\)-hexane \(>\) ethyne
2 \(n\)-Hexane \(>\) benzene \(>\) ethyne
3 Ethyne \(>n\)-hexane \(>\) benzene
4 Ethyne \(>\) benzene \(>n\)-hexane
Explanation:
(d) Acidity order:
Acidity \(\propto \frac{1}{\mathrm{pK}_{\mathrm{a}}}\)
Ethyne \(>\) Benzene \(>n-\) Hexane
\(\mathrm{pK}_a \approx 25 \mathrm{pK}_a \approx 43 \quad \mathrm{pK}_a \approx 50\)
Carbon in ethyne is \(s p\), in benzene \(s p^2\) while in \(n\) hexane \(s p^3\) hybridised, and acidity increases with increase in percentage of \(s\) character.
Karnataka CET 2021
CHEMISTRY(KCET)
285329
Peroxide effectis observed with the addition of HBr but not with the addition of HI to unsymmetrical alkene because
1 \(\mathrm{H}-\mathrm{I}\) bond is stronger than \(\mathrm{H}-\mathrm{Br}\) and is not cleayed by the free radical
2 \(\mathrm{H}-\mathrm{I}\) bond is weaker than \(\mathrm{H}-\mathrm{Br}\) bond so that iodine free radical combine to form iodine molecules
3 bond strength of HI and HBr are same but free radicals are formed in HBr
4 all of these.
Explanation:
(b)\(\mathrm{H}-\mathrm{I}\) bond is weaker \((296.8 \mathrm{~kJ} / \mathrm{mol})\) than \(\mathrm{H}-\mathrm{Br}\) ( \(363.7 \mathrm{~kJ} / \mathrm{mol}\) ) and iodine free radicals combine to form iodine molecules instead of adding to double bond.
Karnataka CET 2021
CHEMISTRY(KCET)
285330
Identify '\(X\) ' in the following reaction.
\(\text { (excess) }+6 \mathrm{Cl}_2 \xrightarrow[\text { dark, cold }]{\text { Anhydrous } \mathrm{AlCl}_3} \mathrm{X}+6 \mathrm{HCl}\)
Ans:a
Exp:(a)
285325
Among the following:
I
II
III
IV
V
The set which represents aromatic species is
1 I, II and III
2 III, IV and IV
3 II and III
4 I, II and IV
Explanation:
(d) Aromatic species :- ( \(4 \mathrm{n}+2 \pi\) electrons)I
II
Anti-aromatic : - ( \(4 \mathrm{n} \pi\) electrons)
III
V
Karnataka CET 2023
CHEMISTRY(KCET)
285328
Arrange benzene,\(n\)-hexane and ethyne in decreasing order of their acidic behaviour.
1 Benzene\(>n\)-hexane \(>\) ethyne
2 \(n\)-Hexane \(>\) benzene \(>\) ethyne
3 Ethyne \(>n\)-hexane \(>\) benzene
4 Ethyne \(>\) benzene \(>n\)-hexane
Explanation:
(d) Acidity order:
Acidity \(\propto \frac{1}{\mathrm{pK}_{\mathrm{a}}}\)
Ethyne \(>\) Benzene \(>n-\) Hexane
\(\mathrm{pK}_a \approx 25 \mathrm{pK}_a \approx 43 \quad \mathrm{pK}_a \approx 50\)
Carbon in ethyne is \(s p\), in benzene \(s p^2\) while in \(n\) hexane \(s p^3\) hybridised, and acidity increases with increase in percentage of \(s\) character.
Karnataka CET 2021
CHEMISTRY(KCET)
285329
Peroxide effectis observed with the addition of HBr but not with the addition of HI to unsymmetrical alkene because
1 \(\mathrm{H}-\mathrm{I}\) bond is stronger than \(\mathrm{H}-\mathrm{Br}\) and is not cleayed by the free radical
2 \(\mathrm{H}-\mathrm{I}\) bond is weaker than \(\mathrm{H}-\mathrm{Br}\) bond so that iodine free radical combine to form iodine molecules
3 bond strength of HI and HBr are same but free radicals are formed in HBr
4 all of these.
Explanation:
(b)\(\mathrm{H}-\mathrm{I}\) bond is weaker \((296.8 \mathrm{~kJ} / \mathrm{mol})\) than \(\mathrm{H}-\mathrm{Br}\) ( \(363.7 \mathrm{~kJ} / \mathrm{mol}\) ) and iodine free radicals combine to form iodine molecules instead of adding to double bond.
Karnataka CET 2021
CHEMISTRY(KCET)
285330
Identify '\(X\) ' in the following reaction.
\(\text { (excess) }+6 \mathrm{Cl}_2 \xrightarrow[\text { dark, cold }]{\text { Anhydrous } \mathrm{AlCl}_3} \mathrm{X}+6 \mathrm{HCl}\)
Ans:a
Exp:(a)
285325
Among the following:
I
II
III
IV
V
The set which represents aromatic species is
1 I, II and III
2 III, IV and IV
3 II and III
4 I, II and IV
Explanation:
(d) Aromatic species :- ( \(4 \mathrm{n}+2 \pi\) electrons)I
II
Anti-aromatic : - ( \(4 \mathrm{n} \pi\) electrons)
III
V
Karnataka CET 2023
CHEMISTRY(KCET)
285328
Arrange benzene,\(n\)-hexane and ethyne in decreasing order of their acidic behaviour.
1 Benzene\(>n\)-hexane \(>\) ethyne
2 \(n\)-Hexane \(>\) benzene \(>\) ethyne
3 Ethyne \(>n\)-hexane \(>\) benzene
4 Ethyne \(>\) benzene \(>n\)-hexane
Explanation:
(d) Acidity order:
Acidity \(\propto \frac{1}{\mathrm{pK}_{\mathrm{a}}}\)
Ethyne \(>\) Benzene \(>n-\) Hexane
\(\mathrm{pK}_a \approx 25 \mathrm{pK}_a \approx 43 \quad \mathrm{pK}_a \approx 50\)
Carbon in ethyne is \(s p\), in benzene \(s p^2\) while in \(n\) hexane \(s p^3\) hybridised, and acidity increases with increase in percentage of \(s\) character.
Karnataka CET 2021
CHEMISTRY(KCET)
285329
Peroxide effectis observed with the addition of HBr but not with the addition of HI to unsymmetrical alkene because
1 \(\mathrm{H}-\mathrm{I}\) bond is stronger than \(\mathrm{H}-\mathrm{Br}\) and is not cleayed by the free radical
2 \(\mathrm{H}-\mathrm{I}\) bond is weaker than \(\mathrm{H}-\mathrm{Br}\) bond so that iodine free radical combine to form iodine molecules
3 bond strength of HI and HBr are same but free radicals are formed in HBr
4 all of these.
Explanation:
(b)\(\mathrm{H}-\mathrm{I}\) bond is weaker \((296.8 \mathrm{~kJ} / \mathrm{mol})\) than \(\mathrm{H}-\mathrm{Br}\) ( \(363.7 \mathrm{~kJ} / \mathrm{mol}\) ) and iodine free radicals combine to form iodine molecules instead of adding to double bond.
Karnataka CET 2021
CHEMISTRY(KCET)
285330
Identify '\(X\) ' in the following reaction.
\(\text { (excess) }+6 \mathrm{Cl}_2 \xrightarrow[\text { dark, cold }]{\text { Anhydrous } \mathrm{AlCl}_3} \mathrm{X}+6 \mathrm{HCl}\)
Ans:a
Exp:(a)
285325
Among the following:
I
II
III
IV
V
The set which represents aromatic species is
1 I, II and III
2 III, IV and IV
3 II and III
4 I, II and IV
Explanation:
(d) Aromatic species :- ( \(4 \mathrm{n}+2 \pi\) electrons)I
II
Anti-aromatic : - ( \(4 \mathrm{n} \pi\) electrons)
III
V
Karnataka CET 2023
CHEMISTRY(KCET)
285328
Arrange benzene,\(n\)-hexane and ethyne in decreasing order of their acidic behaviour.
1 Benzene\(>n\)-hexane \(>\) ethyne
2 \(n\)-Hexane \(>\) benzene \(>\) ethyne
3 Ethyne \(>n\)-hexane \(>\) benzene
4 Ethyne \(>\) benzene \(>n\)-hexane
Explanation:
(d) Acidity order:
Acidity \(\propto \frac{1}{\mathrm{pK}_{\mathrm{a}}}\)
Ethyne \(>\) Benzene \(>n-\) Hexane
\(\mathrm{pK}_a \approx 25 \mathrm{pK}_a \approx 43 \quad \mathrm{pK}_a \approx 50\)
Carbon in ethyne is \(s p\), in benzene \(s p^2\) while in \(n\) hexane \(s p^3\) hybridised, and acidity increases with increase in percentage of \(s\) character.
Karnataka CET 2021
CHEMISTRY(KCET)
285329
Peroxide effectis observed with the addition of HBr but not with the addition of HI to unsymmetrical alkene because
1 \(\mathrm{H}-\mathrm{I}\) bond is stronger than \(\mathrm{H}-\mathrm{Br}\) and is not cleayed by the free radical
2 \(\mathrm{H}-\mathrm{I}\) bond is weaker than \(\mathrm{H}-\mathrm{Br}\) bond so that iodine free radical combine to form iodine molecules
3 bond strength of HI and HBr are same but free radicals are formed in HBr
4 all of these.
Explanation:
(b)\(\mathrm{H}-\mathrm{I}\) bond is weaker \((296.8 \mathrm{~kJ} / \mathrm{mol})\) than \(\mathrm{H}-\mathrm{Br}\) ( \(363.7 \mathrm{~kJ} / \mathrm{mol}\) ) and iodine free radicals combine to form iodine molecules instead of adding to double bond.
Karnataka CET 2021
CHEMISTRY(KCET)
285330
Identify '\(X\) ' in the following reaction.
\(\text { (excess) }+6 \mathrm{Cl}_2 \xrightarrow[\text { dark, cold }]{\text { Anhydrous } \mathrm{AlCl}_3} \mathrm{X}+6 \mathrm{HCl}\)
Ans:a
Exp:(a)
285325
Among the following:
I
II
III
IV
V
The set which represents aromatic species is
1 I, II and III
2 III, IV and IV
3 II and III
4 I, II and IV
Explanation:
(d) Aromatic species :- ( \(4 \mathrm{n}+2 \pi\) electrons)I
II
Anti-aromatic : - ( \(4 \mathrm{n} \pi\) electrons)
III
V
Karnataka CET 2023
CHEMISTRY(KCET)
285328
Arrange benzene,\(n\)-hexane and ethyne in decreasing order of their acidic behaviour.
1 Benzene\(>n\)-hexane \(>\) ethyne
2 \(n\)-Hexane \(>\) benzene \(>\) ethyne
3 Ethyne \(>n\)-hexane \(>\) benzene
4 Ethyne \(>\) benzene \(>n\)-hexane
Explanation:
(d) Acidity order:
Acidity \(\propto \frac{1}{\mathrm{pK}_{\mathrm{a}}}\)
Ethyne \(>\) Benzene \(>n-\) Hexane
\(\mathrm{pK}_a \approx 25 \mathrm{pK}_a \approx 43 \quad \mathrm{pK}_a \approx 50\)
Carbon in ethyne is \(s p\), in benzene \(s p^2\) while in \(n\) hexane \(s p^3\) hybridised, and acidity increases with increase in percentage of \(s\) character.
Karnataka CET 2021
CHEMISTRY(KCET)
285329
Peroxide effectis observed with the addition of HBr but not with the addition of HI to unsymmetrical alkene because
1 \(\mathrm{H}-\mathrm{I}\) bond is stronger than \(\mathrm{H}-\mathrm{Br}\) and is not cleayed by the free radical
2 \(\mathrm{H}-\mathrm{I}\) bond is weaker than \(\mathrm{H}-\mathrm{Br}\) bond so that iodine free radical combine to form iodine molecules
3 bond strength of HI and HBr are same but free radicals are formed in HBr
4 all of these.
Explanation:
(b)\(\mathrm{H}-\mathrm{I}\) bond is weaker \((296.8 \mathrm{~kJ} / \mathrm{mol})\) than \(\mathrm{H}-\mathrm{Br}\) ( \(363.7 \mathrm{~kJ} / \mathrm{mol}\) ) and iodine free radicals combine to form iodine molecules instead of adding to double bond.
Karnataka CET 2021
CHEMISTRY(KCET)
285330
Identify '\(X\) ' in the following reaction.
\(\text { (excess) }+6 \mathrm{Cl}_2 \xrightarrow[\text { dark, cold }]{\text { Anhydrous } \mathrm{AlCl}_3} \mathrm{X}+6 \mathrm{HCl}\)
Ans:a
Exp:(a)
