Is 1-methylpropene a separate butene isomer?

[kelvin macks]

this website only shows 5 isomer for butene. which is 1-butene, 2-butene(cis and trans), 2-methylpropene, cyclobutane. but i have 1 extra compared to the website which is 1-methyl-propene. I correct or the website correct?

http://www.ausetute.com.au/namisene.html

 

[Borek]

1-methyl-propene is equivalent of either 1-butene or 2-butene. I am not sure of which, as it is not clear to me where do you want to put the methyl.

 

[tadchem]

Putting the methyl on the #1 carbon of the propene makes the carbon skeleton 4 carbons long and linear - the same as 2-butene.

 

[kelvin macks]

1-methyl-propene is equivalent of either 1-butene or 2-butene. I am not sure of which, as it is not clear to me where do you want to put the methyl.

here's is it. I'm not sure whether the name is correct or not.

 

[Borek]

And how the structure in your image is different from butene-1?

 

[tadchem]

The names seems to be confused about exactly which carbon on the propene skeleton is the #1 carbon.
By convention, the #1 carbon in propene is the one on the end that has the double bond to its neighbor.
That said, you have attached a substituent group (methyl) to the #3 carbon, not the #1 carbon.
If the substituent were anything that did not have a carbon attaching to the propene, then the nomenclature should be somethhing like 3-[substituent]propene.
For example 3-bromopropene or 3-ethoxypropene.
Since you have attached another carbon to the 3-carbon chain of the propene, your carbon skeleton is now longer, and the name propene no longer applies.