101.
What is the carbon-carbon bond length in benzene?
A
$$1.20\,\mathop {\text{A}}\limits^{\text{o}} {\text{ and 1}}{\text{.31}}\,\mathop {\text{A}}\limits^{\text{o}} $$
B
$$1.39\,\mathop {\text{A}}\limits^{\text{o}} $$
C
$$1.39\,\mathop {\text{A}}\limits^{\text{o}} {\text{ and }}1.20\,\mathop {\text{A}}\limits^{\text{o}} $$
D
$$1.20\,\mathop {\text{A}}\limits^{\text{o}} $$
Answer :
$$1.39\,\mathop {\text{A}}\limits^{\text{o}} $$
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Due to resonance all $$C - C$$ bonds are of equal length in benzene.
102.
Choose the correct alkyne and reagents for the preparation of
A
\[,HgS{{O}_{4}},{{H}_{2}}S{{O}_{4}},{{H}_{2}}O\]
B
\[,HgS{{O}_{4}},{{H}_{2}}S{{O}_{4}},{{H}_{2}}O\]
C
\[,B{{H}_{3}},{{H}_{2}}{{O}_{2}},NaOH\]
D
\[,B{{H}_{3}},{{H}_{2}}{{O}_{2}},NaOH\]
Answer :
\[,HgS{{O}_{4}},{{H}_{2}}S{{O}_{4}},{{H}_{2}}O\]
103.
Which one of these, is not compatible with arenes?
A
Greater stability
B
Delocalisation of $$\pi $$ -electrons
C
Electrophilic additions
D
Resonance
Answer :
Electrophilic additions
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Arenes gives an electrophilic substitution reactions. They do not give electrophilic addition reaction in normal state due to resonance stabilisation.
104.
The correct trend of acidic nature of the following alkynes is
A
$$CH \equiv CH > C{H_3} - C \equiv $$ $$CH > C{H_3}C \equiv CC{H_3}$$
B
$$C{H_3} - C \equiv CH > CH \equiv $$ $$CH > C{H_3}C \equiv CC{H_3}$$
C
$$C{H_3}C \equiv CC{H_3} > C{H_3} - C \equiv $$ $$CH > CH \equiv CH$$
D
$$CH \equiv CH > C{H_3}C \equiv $$ $$CC{H_3} > C{H_3}C \equiv CH$$
Answer :
$$CH \equiv CH > C{H_3} - C \equiv $$ $$CH > C{H_3}C \equiv CC{H_3}$$
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No explanation is given for this question. Let's discuss the answer together.
106.
Which of the following molecules is least resonance stabilized ?
A
B
C
D
Answer :
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is non-aromatic and hence least resonance
stabilized,
whereas other three are aromatic and resonance
stabilized.
107.
The major product of the following reaction is :
\[C{{H}_{3}}C\equiv CH\xrightarrow[\left( \text{ii} \right)\,\,Dl]{\left( \text{i} \right)\,\,DCl\text{(lequiv}\text{.)}}\]
A
\[C{{H}_{3}}CD\left( I \right)CHD\left( Cl \right)\]
B
\[C{{H}_{3}}CD\left( Cl \right)CHD\left( I \right)\]
C
\[C{{H}_{3}}C{{D}_{2}}CH\left( Cl \right)\left( I \right)\]
D
\[C{{H}_{3}}C\left( I \right)\left( Cl \right)CH{{D}_{2}}\]
Answer :
\[C{{H}_{3}}C\left( I \right)\left( Cl \right)CH{{D}_{2}}\]
108.
Match the column I with column II and mark the appropriate choice.
Column I
Column II
a.
$$n$$ - Butane $$ \to $$ 2 - Methylpropane
1.
Free radical substitution
b.
\[C{{H}_{4}}+C{{l}_{2}}\xrightarrow{h\upsilon }C{{H}_{3}}Cl\]
2.
Wurtz reaction
c.
$$RCOONa\, + $$ soda lime $$ \to RH$$
3.
Isomerisation
d.
\[RX+Na\xrightarrow{\text{ether}}R-R\]
4.
Decarboxylation
A
a - 3, b - 1, c - 4, d - 2
B
a - 2, b - 4, c - 1, d - 3
C
a - 1, b - 2, c - 4, d - 3
D
a - 4, b - 1, c - 3, d - 2
Answer :
a - 3, b - 1, c - 4, d - 2
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109.
A compound is treated with $$NaN{H_2}$$ to give sodium salt. Identify the compound.
A
$${C_2}{H_2}$$
B
$${C_6}{H_6}$$
C
$${C_2}{H_6}$$
D
$${C_2}{H_4}$$
Answer :
$${C_2}{H_2}$$
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Sodamide is strong base. Therefore it attracts the more acidic hydrogen and gives sodium salt
$$H - C \equiv C - H + NaN{H_2} \to $$ $$\mathop {H - C \equiv {C^ - }N{a^ + }}\limits_{{\text{Sodium ethynide}}} + \frac{1}{2}{H_2}$$
110.
In preparation of alkene from alcohol using $$A{l_2}{O_3}$$ which is effective factor ?
A
Porosity of $$A{l_2}{O_3}$$
B
Temperature
C
Concentration
D
Surface area of $$A{l_2}{O_3}$$
Answer :
Surface area of $$A{l_2}{O_3}$$
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The amount of alcohol absorbed depends upon the surface area of $$A{l_2}{O_3}$$