[kellykell]

how would you name this carboxylic acid?
CH3CH2CH(COOH)CH3

is it 2-methylbutanoic acid?

[azmanam]

yes.

[jheelan]

My professor has suggested that the common name for 2-methypropene should be isobutylene, not  isobutene.  It's my understanding the "alkylene" nomenclature is older and that alkenes should be named by dropping the '-ane' and adding an '-ene'.  If this is the case then isobutane becomes isobutene.  Does anyone have any thoughts on this?

[azmanam]

Either 2-methylpropene or isobutylene is fine.  IUPAC says 2-methylpropene.  Any chemist 'skilled in the art' will know what isobutylene is.  Isobutene doesn't really work, though - but people would probably still know what you're talking about.

[jheelan]

Ok I'll accept that, but why doesn't it work?  I see isobutene alot in literature.  What about ethylene and propylene?  My chem prof taught us that these were incorrect.  I'm confused.

[azmanam]

yeah, after googling, I guess isobutene is ok.  I still contend 2-methylpropene is the offiical IUPAC name, and isobutylene is the 'official' common name, although we could have a good faith disagreement.  I'd know what you were talking about if you said isobutene, though.  thing with common names is there is no rules.  So if you get enough people to call it jheelan's reagent, it would be an accepted common name, too.

ethylene and propylene are also the accepted common names.  again, IUPAC disagrees and says ethene and propene.  so if you're professor was being strict and only teaching you IUPAC names (which I don't have a problem with, because it's very systematic for simple compounds and there's no ambiguity for simple compounds), then common names would have been incorrect answers.  common names do not conform to iupac rules, and a professor strictly teaching iupac names would take points off.

hope i didn't confuse things even more

[jheelan]

I think you've cleared it up.  Thanks!