Organic Chemistry - IUPAC Naming Doubt

Question

I have a doubt in Organic compounds IUPAC naming..While naming these my teacher says that the bond's (double or triple) position should be of the least number which means counting from the side it is closer to. But, I learnt from the internet while naming hydrocarbons the -yl group(ethyl, methyl, propyl,etc) attachment's number should be the least (i mean count from the side the theyl group attachment is closest)......So should we keep the bond's number the least or the carbon on which the -yl group is attached the least?! Plz help! Exams in 3 days!

Answer 1

Hello Dozer, your teacher is right.  When numbering the carbon atoms of the longest carbon chain, we do so to give a double or triple bond the lowest possible number.  Then you number the substituent functional groups in alphabetical order.  There should be plenty of examples in your text book.

 

All the best,

Randall