[Sharg]

Hi,

I'm a first semester intro to Organic Chem student and I am having a lot of problems with naming Alkenes/Alkynes when you are given a structural or a skeleton formula.
One example I'm having trouble with, is this,



Here is where I am having trouble. For question 1, I know you need to count the number of carbons to know which name to use, but where is the correct place to start? I can see three methyl groups (H3C and CH3) and a hydrogen. My initial thinking was that this is a methene (Two C's with a double bond) with three attached methyl groups, but that turned out to be the wrong answer. Apparently, this is a butane (4 carbons) but I don't understand how one counts 4 Carbons in this, do you count one of the methyl groups as part of the chain?

The following two problems I couldn't get right either, but I think if someone can help me with the concept of naming Alkenes in general, I'll be able to do it. I tried to google it, but I can't seem to grasp it, even watching Khan Academy videos...

Thank you in advance.

[Ben Bob2]

The two rules that are the foundation of naming alkenes are as follows:
1) Count the longest continuous chain of carbon atoms that contains both atoms in the double bond
2) Number the chain beginning from the end that is closest to the double bond

From your attempt, it looks like you are counting beginning with the double bond which isn't correct in this case. You always need to count  from a terminal carbon.

Just start counting from one methyl, to the double bond, and then to the other methyl and you have a butene.

Try it again and see what you get.

[Sharg]

Ohhh I think I get it now...doing much better on practice alkene naming problems now.
Thanks A MILLION! This seems soo much easier now.