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Question
Draw the cis and trans structures of hex-2-ene. Which isomer will have higher b.p. and why?
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Solution
Hex-2-ene is represented as:
\[\ce{CH3 - CH = CH - CH2 - CH2 - CH3}\]
Geometrical isomers of hex-2-ene are:
\[\begin{array}{cc}
\phantom{.............}\ce{H3C}\phantom{.........}\ce{CH2 - CH2 - CH3}\\
\backslash\phantom{.......}/\\
\ce{C = C}\\
/\phantom{.......}\backslash\\
\ce{H}\phantom{.........}\ce{H}\end{array}\]
cis-isomer
\[\begin{array}{cc}
\phantom{.}\ce{H3C}\phantom{......}\ce{H}\\
\backslash\phantom{.......}/\\
\ce{C = C}\\
/\phantom{.......}\backslash\\
\phantom{..............}\ce{H}\phantom{.......}\ce{CH2 - CH2 - CH3}\end{array}\]
trans-isomer
The dipole moment of cis-compound is a sum of the dipole moments of C–CH3 and C–CH2CH2CH3 bonds acting in the same direction.
The dipole moment of trans-compound is the resultant of the dipole moments of C–CH3 and C–CH2CH2CH3 bonds acting in opposite directions.
Hence, cis-isomer is more polar than trans-isomer. The higher the polarity, the greater is the intermolecular dipole-dipole interaction and the higher will be the boiling point. Hence, cis-isomer will have a higher boiling point than trans-isomer.
RELATED QUESTIONS
Write IUPAC name of the product obtained by the ozonolysis of the following compound:
3,4-Dimethyl-hept-3-ene
Write IUPAC name of the product obtained by the ozonolysis of the following compound:
2-Ethylbut-1-ene
What effect does branching of an alkane chain has on its boiling point?
What is the relationship between the members of following pairs of structures? Are they structural or geometrical isomers or resonance contributors?
\[\begin{array}{cc}
\ce{D}\phantom{......}\ce{H}\\
\backslash\phantom{......}/\\
\ce{C = C}\\
\phantom{...}/\phantom{......}\backslash\phantom{...}\\\ce{H}\phantom{.......}\ce{D}
\end{array}\]
\[\begin{array}{cc}
\ce{D}\phantom{......}\ce{D}\\
\backslash\phantom{......}/\\
\ce{C = C}\\
\phantom{...}/\phantom{......}\backslash\phantom{...}\\\ce{H}\phantom{.......}\ce{H}\end{array}\]
Find out the type of isomerism exhibited by the following pair.
\[\begin{array}{cc}
\ce{CH3 - CH - CH2 - CH3 and CH3 - CH2 - O - CH2 - CH3}\\|\phantom{...........................................}\\
\ce{OH}\phantom{.........................................}\end{array}\]
Find out the type of isomerism exhibited by the following pair.
Choose the correct option.
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What is the relationship between the members of following pairs of structures? Are they structural or geometrical isomers or resonance contributors?
Consider structures I to VII and answer the question:
| I. | CH3 – CH2 – CH2 – CH2 – OH |
| II. | \[\begin{array}{cc} \ce{CH3 - CH2 - CH - CH3}\\ \phantom{.....}|\\ \phantom{.......}\ce{OH} \end{array}\] |
| III. | \[\begin{array}{cc} \phantom{...}\ce{CH3}\\ \phantom{}|\\ \ce{CH3 - C - CH3}\\ \phantom{}|\\ \phantom{..}\ce{OH} \end{array}\] |
| IV. | \[\begin{array}{cc} \ce{CH3 - CH - CH2 - OH}\\ |\phantom{........}\\ \ce{CH3}\phantom{......} \end{array}\] |
| V. | CH3 – CH2 – O – CH2 – CH3 |
| VI. | CH3 – O – CH2 – CH2 – CH3 |
| VII. | \[\begin{array}{cc} \ce{CH3 - O - CH - CH3}\\ \phantom{...}|\\ \phantom{......}\ce{CH3} \end{array}\] |
Identify the pairs of compounds which are functional group isomers.
Consider structures I to VII and answer the question:
| I. | CH3 – CH2 – CH2 – CH2 – OH |
| II. | \[\begin{array}{cc} \ce{CH3 - CH2 - CH - CH3}\\ \phantom{.....}|\\ \phantom{.......}\ce{OH} \end{array}\] |
| III. | \[\begin{array}{cc} \phantom{...}\ce{CH3}\\ \phantom{}|\\ \ce{CH3 - C - CH3}\\ \phantom{}|\\ \phantom{..}\ce{OH} \end{array}\] |
| IV. | \[\begin{array}{cc} \ce{CH3 - CH - CH2 - OH}\\ |\phantom{........}\\ \ce{CH3}\phantom{......} \end{array}\] |
| V. | CH3 – CH2 – O – CH2 – CH3 |
| VI. | CH3 – O – CH2 – CH2 – CH3 |
| VII. | \[\begin{array}{cc} \ce{CH3 - O - CH - CH3}\\ \phantom{...}|\\ \phantom{......}\ce{CH3} \end{array}\] |
Identify the pairs of compounds that represents position isomerism.
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| I. | CH3 – CH2 – CH2 – CH2 – OH |
| II. | \[\begin{array}{cc} \ce{CH3 - CH2 - CH - CH3}\\ \phantom{.....}|\\ \phantom{.......}\ce{OH} \end{array}\] |
| III. | \[\begin{array}{cc} \phantom{...}\ce{CH3}\\ \phantom{}|\\ \ce{CH3 - C - CH3}\\ \phantom{}|\\ \phantom{..}\ce{OH} \end{array}\] |
| IV. | \[\begin{array}{cc} \ce{CH3 - CH - CH2 - OH}\\ |\phantom{........}\\ \ce{CH3}\phantom{......} \end{array}\] |
| V. | CH3 – CH2 – O – CH2 – CH3 |
| VI. | CH3 – O – CH2 – CH2 – CH3 |
| VII. | \[\begin{array}{cc} \ce{CH3 - O - CH - CH3}\\ \phantom{...}|\\ \phantom{......}\ce{CH3} \end{array}\] |
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Reason (R): Position isomers differ in the position of functional group or a substituent.
The molecules having dipole moment are:
(i) 2,2-Dimethylpropane
(ii) trans-Pent-2-ene
(iii) cis-Hex-3-ene
(iv) 2, 2, 3, 3 - Tetramethylbutane.
Assertion (A): The compound cyclooctane has the following structural formula: 
It is cyclic and has conjugated 8π-electron system but it is not an aromatic compound.
Reason (R): (4n + 2)π electrons rule does not hold good and ring is not planar.
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The correct stereochemical name of
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