[jennielynn_1980]

I am learning to name hydrocarbons and I have these two to name:

a)  CH₃ - C = CH - CH₂ - CH₃
               |
             CH₃

For this one I know it's a pentene (5 carbons in longest chain with one double bond at carbon 2)  I know that it has a methyl group on the 2nd carbon.  So would it be called
2-methylpentene-2?

b)                 Cl
                      |
     CH₃ - C = C - CH₂ - CH₃
               |
              Cl

This one I am struggling with because of the chlorine.  We haven't named these ones before.  Because there are 5 carbons in the longest chain and it has one double bond at carbon 2 it is a pentene.  There are chlorines at carbons 2 and 3 so dichloro.  My answer here is
2,3 - dichloropentene - 2.  This one is a BIG guess with the name.

Thanks

[enahs]

  So would it be called
2-methylpentene-2?

Not quite.
2-methylpent-2-ene
Or
2-methyl-2-pentene

2,3 - dichloropentene - 2.  This one is a BIG guess with the name.

Not quite, but again same simple mistake (getting the name correct, but writing it wrong following standards). But your reasoning for the name is sound.
2,3-dichloropent-2-ene

But now, ahah! You have a double bond, this means it can be sis or trans (or E-Z if you covered that?)
So now you must determine if the chlorines on the 2nd and 3rd are cis or trans to each other, then tack that on to the beginning of the name. I am assuming you have talked about cis-tran? If not, then just ignore it.

Also, you put some spaces between the dash sometimes, there is not such space following the IUPAC nomenclature standards, at least, not in these cases.

[jennielynn_1980]

Okay, so the second one would be trans-2,3-dichloro-2-pentene?

Thanks for the help:)

[english]

Okay, so the second one would be trans-2,3-dichloro-2-pentene?

Thanks for the help:)

Yes 

Remember though Jennie that if one side of the alkene double bond has identical substituents, then there cannot be any trans or cis isomerisim. 


For example,

                    Cl
                    |
    CH3 - C = C - CH2 - CH3
               |
              CH₃

is niether cis nor trans.

[jennielynn_1980]

Thanks for your help   and the tip on trans cis isomerism