10) That's right, the main chain is decane. There are three different groups attached to the main chain, an ethyl group, an isopropyl group, and a methyl group. Since there is a group closest to the left end, we number starting from that end. The ethyl group is on carbon 3, the isopropyl group is on carbon 5, and the methyl group is on carbon 7. So, the name is 3-ethyl-5-isopropyl-7-methyldecane. 1) Correct 
2) This is 2,2-dibromobutane.
3) Correct 5) Correct
6) This is 4-ethyl-2-methyloctane. There is a methyl group on carbon 2 and an ethyl group on carbon 4. In the name, the groups are named in alphabetical order.
Whenever you have more than one of any group, you indicate the number with the prefixes di, tri, etc. For example, 1,2,3-trichlorobutane. This name tells us clearly that there are three chloro groups, and one is attached to carbon 1, another on carbon 2, and another on carbon 3. And of course that is the purpose of this naming system, to be able to tell with certainty what the structure of the molecule is, from the name.
Keep at it!
Steve |
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