non-IUPAC names

[Sarahisme]

tis understandable

[chemi]

hey , i can't see why this is called

 

2-Methylethyl

 

or why it is then called ISOPROPYl

 

if someone has the time, could the please explain this too me ?

 

Isopropyl is a term in organic chemistry to refer to a three carbon structure.

It is a variant of propyl, which refers to three carbons added at one end(triple bonds).

 

By contrast, isopropyl refers to a three carbon structure that is attached in the middle. iso (means both sides are equal/balanced) For example, in isopropyl alcohol: (I can't get the image, but you can check out the website)

 

http://en.wikipedia.org/wiki/Isopropyl

 

 

... the '-OH' alcohol functional group is added at the middle of the three carbon structure. (It may seem counterintuitive to name the molecule based upon such a small part of it, but by the rules of organic chemistry nomenclature, alcohols are higher priorities than alkenes, so the three carbon group is interpreted as a substituent of the alcohol.

[chemi]

I guess this would be like 2-isopropyl alcohol but couldn't it be called 2-Propanol? Seems like a easyer name to me

 

iso means equal/balance # of carbons and hydrogens on both sides, since propyl contains 3 carbons, the triple bond must be in the 2nd carbon (in the middle) no matter which way you start to count it, it's always going to be the 2nd carbon. That's why we don't need to put the 2- there. (isopropyl is the exception)

[EwenM]

This 'isopropyl alcohol' stuff was a 1960s attempt to make systematic names and it's still widely used although the systematic names have moved on.

 

'iso' refers to 'isomer' not 'equal'. For example 'isobutyl alcohol' is what we now should be calling butan-2-ol.

 

'Methyl', 'ethyl', 'propyl' etc are the names for an alkane chain attached to the main structure by its first carbon. The old system used to add an 'n-' for these simple chain e.g. 'n-butyl alcohol' (butan-1-ol). The '-yl' ending has nothing to do with the '-yne' ending that denotes a triple bond.

 

The old system for a branch with, say, four carbon atoms was to call the branch 'butyl' and then add 'n-' if the branch was attached by its first carbon and 'iso' (or 'i-') if it was attached by its second carbon. If the branch was itself branched then it was called 'tertiary-', 'tert-' or just plain 't-'.

 

To take nonane as an example (we need 9 carbons in the main chain so that the butyl sidechain is not considered as the mainchain):

 

Modern name Older name

butylnonane n-butyl nonane

(1-methylpropyl)nonane isobutyl nonane

(dimethylethyl)nonane t-butyl nonane

 

Note that brackets are used to indicate that, for example the methyl in (1-methylpropyl)nonane is attached to carbon-1 of the propyl sidechain, not to carbon-1 of the nonane.