General Organic Chemistry MCQ Questions & Answers in Organic Chemistry | Chemistry
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321.
The bond order of individual carbon-carbon bonds in
benzene is
A
one
B
two
C
between one and two
D
one and two alternately
Answer :
between one and two
NOTE:
The phenomenon of resonance gives identical bonding
and hence identical bond lengths.
$$C - C$$ bond order in benzene = 1.5
322.
The principle involved in paper chromatography is
A
adsorption
B
partition
C
solubility
D
volatility
Answer :
partition
Paper chromatography is a type of partition chromatography which is based on the principle of continuous differential partitioning of components of a mixture between stationary and mobile phases.
323.
Which one of the following orders is correct regarding the $$-I$$ -effect of the substituents ?
A
$$ - N{R_2} < - OR > - F$$
B
$$ - N{R_2} > - OR > - F$$
C
$$ - N{R_2} < - OR < - F$$
D
$$ - N{R_2} > - OR < - F$$
Answer :
$$ - N{R_2} < - OR < - F$$
The electronegativity follows the order $$N < O < F.$$ So, due to electronegative character the order of $$-I$$ -effect is
$$ - N{R_2} < - OR < - F$$
324.
Which one of the following is most stable ?
A
B
C
D
Answer :
$${3^ \circ }$$ carbocations are most stable.
325.
With respect to the conformers of ethane, which of the following statements is true?
A
Bond angle remains same but bond length changes
B
Bond angle changes but bond length remains same
C
Both bond angle and bond length change
D
Both bond angles and bond length remain same
Answer :
Both bond angles and bond length remain same
Isomers which are possible by rotation about single bonds without cleavage of any bond are called conformers. In ethane, an infinite number of conformations are possible. There are two extreme forms, the staggered conformation, which is the most stable and the eclipsed conformation which is least stable. Among the conformers of ethane, bond angle and bond length remains same while their energy, stability and dihedral angle are different.
326.
Which of the following statements is not correct ?
A
Carbocation posses sextet of electrons.
B
The order of carbocation stability is :
$$\mathop C\limits^ + {H_3} > {\left( {C{H_3}} \right)_2}\mathop C\limits^ + H > {\left( {C{H_3}} \right)_3}\mathop C\limits^ + $$
C
Carbocations have trigonal planar shape
D
Carbocations are formed by heterolytic cleavage
Answer :
The order of carbocation stability is :
$$\mathop C\limits^ + {H_3} > {\left( {C{H_3}} \right)_2}\mathop C\limits^ + H > {\left( {C{H_3}} \right)_3}\mathop C\limits^ + $$
The order of stability of carbocations is :
$${\left( {C{H_3}} \right)_3}\mathop C\limits^ + > {\left( {C{H_3}} \right)_2}\mathop C\limits^ + H > \mathop C\limits^ + {H_3}$$
327.
Which one of the following pairs represents stereoisomerism?
A
Chain isomerism and rotational isomerism
B
Structural isomerism and geometrical isomerism
C
Linkage isomerism and geometrical isomerism
D
Optical isomerism and geometrical isomerism
Answer :
Optical isomerism and geometrical isomerism
Pair of optical isomerism and geometrical isomerism are able to exhibit the phenomenon of stereoisomerism because both type of isomers differ only in their orientation in space.
328.
In an $${S_N}1$$ reaction on chiral centres there is
A
100% racemisation
B
inversion more than retention leading to partial racemisation
C
100% retention
D
100% inversion
Answer :
inversion more than retention leading to partial racemisation
In $${S_N}1$$ reaction, there is slight more inversion product than retention product because $${S_N}1$$ reaction also depend on shielding effect of the front side of the reacting carbon.
329.
Which one of the following does not have $$s{p^2}$$ hybridized
carbon ?
A
Acetonitrile
B
Acetic acid
C
Acetone
D
Acetamide
Answer :
Acetonitrile
330.
Which among the following is substitution reaction ?
A
B
C
D
Answer :
\[{{R}_{3}}COH\xrightarrow[Conc.\,HCl]{Anhy.\,ZnC{{l}_{2}}}{{R}_{3}}C.Cl\]
It is substitution reaction. \[{{R}_{3}}C.Cl\] being insoluble in \[{{H}_{2}}O\] give turbid solution.