Chapter 21 - Exercises - Page 881a: 21

a) 2,2,4-trimethylhexane b) 5-methylnonane c) 2,2,4,4-tetramethylpentane d) 3-ethyl-3-methyloctane

a) Count the no. of C atoms in straight chain. Here it is 6. So, word root is 'hex'. Numbering the C atoms in straight chain from 1 to 6 So that the substituents get the minimum number. So, the numbering will be done from the left side so that two methyl groups at C2 position and one methyl group is at C4 position. So, prefix '2,2,4-trimethyl' is added before 'hex'. Ending name is 'ane' for alkane. b) Count the no. of C atoms in straight chain. Here it is 9. So, word root is 'non'. Numbering the C atoms in straight chain from 1 to 9 So that the substituents get the minimum number. So, the numbering will be done from the either side so that methyl group is at C5 position. So, prefix '5-methyl' is added before 'non'. Ending name is 'ane' for alkane. c) Count the no. of C atoms in straight chain. Here it is 5. So, word root is 'pent'. Numbering the C atoms in straight chain from 1 to 5 So that the substituents get the minimum number. So, the numbering will be done from either side so that two methyl groups will be at C2 position and another two methyl groups will be at C4 position. So, prefix '2,2,4,4-tetramethyl' is added before 'pent'. Ending name is 'ane' for alkane. d) Count the no. of C atoms in longest straight chain. Here it is 8. So, word root is 'oct'. Numbering the C atoms in straight chain from 1 to 8 So that the substituents get the minimum number. So, the numbering will be done from the left side so that one methyl group will be at C3 position and one ethyl group will also be at C3 position. So, prefix '3-ethyl-3-methyl' is added before 'oct'. Ending name is 'ane' for alkane.