Chapter 21 - Exercises - Page 881a: 14

1. hexane 2. 2-methylpentane 3. 3-methylpentane 4. 2,3-dimethylbutane 5.2,2-dimethylbutane.

1. Count the no. of C in straight chain. Here it is 6. So, word root is 'hex'. ending name is 'ane' for alkane. so, the name: hexane. 2. No. of C in straight chain = 5. So, word root is pent. Now, one methyl group is present at C2 position if we numbering the C in straight chain from 1 to 5 (here right to left). so, 2-methyl is added before word root and ending name is 'ane'. so, the name : 2-methylpentane 3. No. of C in straight chain = 5. So, word root is pent. Now, one methyl group is present at C3 position if we numbering the C in straight chain from 1 to 5 (from either side). so, '3-methyl' is added before word root and ending name is 'ane'. so, the name : 3-methylpentane 4. No. of C in straight chain = 4. So, word root is 'but'. Now, two methyl groups are present at C2 and C3 position respectively if we numbering the C in straight chain from 1 to 4. so, '2,3-dimethyl' is added before word root and ending name is 'ane'. so, the name: 2,3-dimethylbutane 5. No. of C in straight chain = 4. So, word root is 'but'. Now, two methyl groups are present at C2 position if we numbering the C in straight chain from 1 to 4. so, '2,2-dimethyl' is added before word root and ending name is 'ane'. so, the name: 2,2-dimethylbutane.