Question

In ncert reader page 335 example there is a compound 5-sec-Butyl-4-isopropyldecane here how come CH3-CH-CH2-CH3 can be called as sec butyl because in the previous pages there is a diferent structure for it and in its name why is there a dash between sec and butyl

Answer 1

The given structure is correct. There is a free valency at the second group (hence there is only one hydrogen, in CH) - this is a substituent group.

It is called sec, since the free valency is a secondary valency (2° carbon), and butyl since it has 4 carbon atoms.

For butyl, you can't possibly draw another substituent group with a secondary valency, so there can't be any clash of, like, what group are we talking about when we say sec-butyl.

The structure is attached below.