1,3-butanol exhibits stereoisomerism, draw appropriate structural formulae of each isomer.?

Question

also how they could be distinguished.

this is a coursework question i got last week however due to time shortage i was not able to ask before handing it in so i want to see if i got this question right or not.

thanks for ur help.

Answer 1

I presume you mean butan-1,3-diol (or 1,3-butanediol) It's not easy to draw structural formulæ in this format, but I'll give it a try !
Basically, the formula is CH3---CH(OH)---CH2---CH2(OH).
The no. 3 carbon atom (the second one, if counting from the left) is the centre of chirality. The best way of representing it would be to draw the skeleton in the plane of the paper:
CH3---C---CH2---CH2---OH.
Remember that the C---C---C angle is about 109°, so the skeleton should form a zig-zag pattern - not a straight line.

Then, for one of the enantiomers, you draw the OH group linked to the no. 3 carbon atom using a heavy, solid line (this being the convention used to mean that it is sticking OUT IN FRONT of the plane of the paper) and you draw the H atom linked to the no. 3 C atom, using a dotted line, to show that it is BEHIND the plane of the paper.

For the other enantiomer, you start off the same way, but link the OH group to the no. 3 C atom by a dotted line and you link the H atom by a solid, heavy line.

In answer to "How could they be distinguished ?" the simplest way would be to place a sample of each of them in turn in the sample tube of a polarimeter. One of the enantiomers will turn polarised light clockwise; the other one will turn polarised light anti-clockwise.

P.S. I've just noticed what Ron B said. His answer is misleading, because the conformation of the OH group on the no. 1 carbon atom has very little to do with the stereoisomerism. This is certainly NOT a case of cis-trans stereoisomerism, but of optical stereoisomerism.

Answer 2

The stereoisomerism will be due to the cis and trans versions of the same formula.

In the "cis" version, the OH groups will be on the same side of the butane skeleton. In the "trans" version they will be on opposite sides.

Answer 3

Did you mean 1,3-Butanediol?

Answer 4

(S)-(+)-1,3-Butanediol: c in this link:

http://www.coleparmer.com/catalog/small_images/AGROS2179
7.jpg

(R)-(-)-1,3-Butanediol: c in this link:


http://www.coleparmer.com/catalog/small_images/AGROS21796.jpg

butanediol is the correct name.