[Byrne]

The question reads...

Why is it impossible for the correct name of a linear alkane to begin with 1-methyl?

I've read my text and tried searching for something on the Internet and can't seem to come up with an answer.  Help.

[Donaldson Tan]

You can't have a methyl group at the first carbon because it would suggest the correct first carbon is actually the carbon atom of the methyl group and not the original carbon atom.

[hmx9123]

Please excuse Geo's rudeness, he's just laughing at the question, not at you.  The idea he's trying to convey is that if you have 1-methyl, you really aren't at the first carbon of your chain.  You necessarily have to have at least one carbon besides the methyl group, i.e., the #1 carbon that you're looking at.  Because the methyl is connected to it, it's one carbon longer than what you anticipated--thus it increases your hydrocarbon length by one.  For example, draw out this structure:

2-pentanol

Now draw this out: (the IUPAC naming is incorrect, but you can figure out what it is)

1-methyl-1-butanol

As you notice, they are the same molecule.  Notice how the 4 carbon chain isn't really the longest carbon chain, so you then have to lengthen the carbon chain to account for it.  Just off the top of my head, I'd say that this rule holds true for any alkyl substituent.  Try it.  Try using ethyl or propyl, draw some name that you came up with, and then see if there's a longer carbon chain that you can use to name it.

[arnyk]

Having the methyl group on the first carbon is basically just making the base chain one carbon longer.  So 1-methylpentane would actually be just hexane.