Organic Chemistry, alkyl groups and structural isomers

[EspoirTron]

Hey guys I was wondering!
In the heinemann book when naming organic molecules the book sometimes includes brackets e.g. (CH2)3, is this just an abbreviation?
Also if I have a molecule say butanoic acid, could a possible structural isomer be methyl propanoic acid?
Does altering the positioning of carbon atoms (i.e. as aforementioned changing it so a carbon has an alkyl group) change the molecules chemical principles? So would chrlororpropane have different chemical properties to say an isomer methyl chroloethane (if that isomer even exists)?
Thank you to whoever can help me! 

[alondouek]

1. (CH₂)₃ is an abbreviation, it's the same thing as .

2. Yes! 2-methyl propanoic acid is an isomer of butanoic acid.

3. Well, functional groups are what dictate how a molecule behaves. If you were to remove one functional group from a molecule and put another functional group in its place, you could definitely change the properties of said molecule.

[EspoirTron]

1. (CH₂)₃ is an abbreviation, it's the same thing as .

2. Yes! 2-methyl propanoic acid is an isomer of butanoic acid.

3. Well, functional groups are what dictate how a molecule behaves. If you were to remove one functional group from a molecule and put another functional group in its place, you could definitely change the properties of said molecule.

Thanks for that!
So changing the position of alkyl groups can indeed render a new structural isomer?

[Limista]

So changing the position of alkyl groups can indeed render a new structural isomer?

Yes, to an extent.

What is an isomer? It is an organic molecule whose molecular formula remains the same, but structural formula changes. Specifically, a structural formula is a 3D arrangement of atoms in the organic molecule. Therefore, if you change the position of an alkyl group on a carbon chain, the 3D arrangement is changing.

That said, draw a butane straight chain isomer. Number the carbon atoms 1-4 from left to right. Initially, the "chloro" alkyl group was bonded to the 1st carbon atom, so you have 1-chlorobutane. If you move this "chloro" alkyl group to the number 4 carbon atom, it is the SAME as having 1-chlorobutane.

[EspoirTron]

Yes, to an extent.

What is an isomer? It is an organic molecule whose molecular formula remains the same, but structural formula changes. Specifically, a structural formula is a 3D arrangement of atoms in the organic molecule. Therefore, if you change the position of an alkyl group on a carbon chain, the 3D arrangement is changing.

That said, draw a butane straight chain isomer. Number the carbon atoms 1-4 from left to right. Initially, the "chloro" alkyl group was bonded to the 1st carbon atom, so you have 1-chlorobutane. If you move this "chloro" alkyl group to the number 4 carbon atom, it is the SAME as having 1-chlorobutane.

That does make a lot of sense, you are quite right there. I think then in that case, I could put on either three of the hydrogens yet it would essentially be the same molecule, thanks for that!