describe the various conformation of 1,2 dimethly cyclohexane in hindi
Answers
Answer:
Discuss the the relative conformation analysis of 1,2-dimethylcyclohexane.
If we consider cis isomer of 1,2-dimethylcyclohexane, the e,a and a,e both conformer is
optically active ads no element of symmetry present. In both conformer three extra gauche
butane interaction present and hence both conformer is equally populated. But on flipping it
gives the mirror image conformer and hence they are enantimers of each other. So due to
internal compensation net optical rotation is zero and they are called invertomer.
Theoritically enantiomers should be separable at very low temperature but in practice there
are no such reports.
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Whereas both the a,a and e,e conformation of trans 1,2-dimethylcyclohexane is optically
active , can exists in enantiomers and they are resolvable . Both the a,a and e,e conformer
contain a C2 axis passing through C1-C2 and C4-C5 bond. It is obvious that in a,a conformer
there is four gauche butane interaction whereas in e,e conformer there is only two gauche
butane interaction and hence the e,e conformer is more stable and maximum populated.
2. Discuss the relative conformation analysis of 1,3-dimethylcyclohexane.
If we look the conformation analysis of cis 1,3-dimethyl cyclohexane, both the e,e and a,a
conformer posses a sigma( σ)plane and hence it is optically inactive; no question of
resolution arises. In a,a conformer there is two extra gauche butane interaction and hence the
e, e conformer is more populated.
In case of trans isomer, both the e,a and a,e conformer contains one extra gauche butane
interaction and hence both conformer is equally populated. But ring invertion itself produces
an equivalent conformer and hence it is an example of topomerisation. The planner structure
Explanation:
symmetry and hence it is asymmetric molecule.
3. Discuss the relative conformation analysis of 1,4-dimethylcyclohexane.
Let us look at the trans isomer of 1,4-dimethylcyclohexane; both the planner structure and
puckered structure contain plane of ymmetry and hence molecule is optically inactive and
hence no question of resolution. The e,e conformer is more stable and highly populated
compared to the a,a confer as the later contain four more gauche butane interaction.
The cis isomer of 1,4-dimethylcyclohexane also contain a sigma plane passing vertically
through C1 and C4 and hence compound is optically inactive; no question of resolution. Both
the e,a and a,e conformers are equally populated and they are equivalent on ring invertion.
4.Discuss the relative stabilities of monosubstituted cyclohexane.
In case of monosubstituted cyclohexane, two different chair conformer exists-with axial
substituents called axial conformer and with equatorial substituents called equatorial
conformer. Both conformers are in rapid equilibrium by means of inversion but they will not
have same energy. In almost all cases, the conformer with axial substituents has higher
energy compared to the equatorial conformer and hence the population percentage of axial
conformer is far less than the equatorial conformer.
H
CH3
CH3
H
H CH3
H3C
H
H CH3
H3C H
H
CH3
CH3
turning upside down 120
rotation H
H
CH3
H
H3C
CH3
H
CH3
H
H
CH3
CH3
H
CH3
H
H
H3C
CH3
H
H
H3C
X
X
high energy conformation low energy conformation
axial substituent:
axial conformer
equatorial substituent:
equatorial conformer