[novi]

hi, i'm having a bit of trouble with a question:

give the structures and names of two branched chain alcohols which are both isomers of butan-1-ol. only isomer 1 is oxidised when warmed with acidified potassium dichromate (VI).



Isomer 1 Name...




(diagram of structure)





Isomer 2 Name.....




(diagram of structure)





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so far all i can guess is that one isomer will be an E isomer adn one a Z... but i'm not entirely sure.. please point me in the right direction or give me the answer please!

[sjb]

How many isomers of butan-1-ol do you know?

How many are alcohols?

[novi]

i dont know how you work that out i just know you have E / Z isomers.. can u help ?

[JimClark]

Sorry if this is too late - I've only just come across it.

This is nothing to do with E/Z isomerism.  That only happens if you have a "locked" molecule, for example with a C=C double bond.

This is about structural isomerism and the reactions of primary, secondary and tertiary alcohols.  You are looking for structural isomers of butan-1-ol.  You could read the Chemguide page http://www.chemguide.co.uk/basicorg/isomerism/structural.html .  The butanol isomers are discussed about 2/3 of the way down the page, but you really ought to read the rest as well.

Then you need to think about how the different kinds of alcohols react (or not) with acidified potassium dichromate(VI) solution.  For that, you could look at http://www.chemguide.co.uk/organicprops/alcohols/oxidation.html

[Donaldson Tan]

Heard of butan-1-ol and butan-2-ol?

[cliverlong]

As a general approach to "generating" isomers within the same homologous group I do the following steps

1. Make as many distinct carbon chains as possible. This means start with the straight chain then introduce branches and side chains. Single C-C bonds can take pretty much any angle in a rough structural diagram and still remain the same molecule. Also rotation about a C-C bond will allow side chains and groups to appear to be in new positions in the diagram where they actually represent the same molecule

2. Place the non-CH groups such as -OH in as many different positions on the chains created in 1. above as possible. Obviously as the number of groups increase there are more potential permutations of position on the chain created in 1.

3. Swap some of the atoms in the groups to create new groups such as converting an -OH to a C=O. Check the molecular formula is still correct and do step 2 again