Q.4-28E - Organic Chemistry (Mcmurry)

Question

Draw two constitutional isomers of $cis-\mathbf{1},\mathbf{2}-\mathbf{dibromocyclopentane}$ .

Step-by-Step Solution

Answer

The two constitutional isomers of cos - 1, 2 - dibromocyclopentane :

Definition of Cis and Trans configuration

Cis configuration is when two groups are on the same face of the ring and trans configuration is when the groups are on opposite faces. 

Both isomers are stable and neither can be converted into the other without breaking and reforming chemical bonds.

Explanation of Constitutional isomers

Constitutional isomers are the molecules that are different in connectivity, the way in which the constituent atoms are connected to one another. They have the same molecular formula but different connectivity.

Rules for the naming of compound

• Find the parent

Count the number of carbon atoms in the ring and the number in the largest substituent whichever has highest carbon atom will be considered as parent. If the number of carbon atoms in the ring is equal to the number in the substituent in that case ring is taken as parent.

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• Number the substituents, and write the name.

For an alkyl- or halo-substituted cycloalkane, choose a point of attachment as carbon 1 and number the substituents on the ring so that the second substituent has as low a number as possible. Same procedure for third or fourth substituent so has low number as much as possible, until a point of difference is found.

 

• When two or more different alkyl groups are present that could potentially take the same numbers, number them by alphabetical priority, ignoring numerical prefixes such as di- and tri-.

 

• If halogens are present, treat them just like alkyl groups.

Structure of two constitutive isomers possible

Structure of the possible or consecutive isomers has been mentioned below here with their respective stereochemistry of the bromine atom