Q4-4-5 - Organic Chemistry (Mcmurry)

Question

Draw the structures of the following molecules: 

(a) trans-1-Bromo-3-methylcyclohexane 

(b) cis-1,2-Dimethylcyclobutane 

(c) trans-1-tert-Butyl-2-ethylcyclohexane

Step-by-Step Solution

Answer

a) 

b) 

c) 

IUPAC nomenclature

It is a method to give a scientific name to the organic compounds recommended by the Indian Union of Pure and Applied Chemistry.

Nomenclature of cycloalkanes

IUPAC rules used for naming of cycloalkanes

• Name the parent cycloalkane 
• Assign numbering to the substituents
• Assign the first number to the bulky group
• Halogens get the first priority
• If both the substituent are on wedge or dash then the cis prefix is used
• If one substituent on the wedge and the other on the dash and vice-versa then the trans prefix is used
• Write the name of the molecule in alphabetic

Structure of cycloalkane (a)

As per the given IUPAC name, we find the structure of the molecule:

1. The parent cycloalkane is cyclohexane
2. The substituents are bromo and methyl
3. Bromo occupies 1 position and methyl occupies 3 position
4. One substituent is on the wedge and the other on the dash so trans configuration
5. Hence, IUPAC is trans-1-bromo,3-methyl cyclohexane
6. So, the structure is shown below:

Naming of cycloalkane (b)

As per the given IUPAC name, we find the structure of the molecule:

1. The parent cycloalkane is cyclobutane
2. The substituent is methyl and methyl
3. Methyl occupies 1 position and methyl occupy 2 position
4. Both substituent is on the wedge so cis configuration
5. Hence, IUPAC is cis-1,2-dimethyl cyclobutane
6. So, the structure is shown below:

Structure of cycloalkane (c)

As per the given IUPAC name, we find the structure of the molecule:

1. The parent cycloalkane is cyclohexane
2. The substituents are tert-butyl and ethyl
3. Tert-butyl occupies 1 position and ethyl occupy 2 position
4. One substituent is on the wedge and the other on the dash so trans configuration
5. Hence, IUPAC is trans-1-tert-butyl,2-ethyl cyclohexane
6. So, the structure as shown below: