optical isomers?

Question

WHAT MAKES A chemical structure..optical isomer?!?!?!?!?!?! how do you count how many there are?!?! please tell me I need to know! thanx!

How many optical isomers does this carbohydrate have?

CH2OH-C=O-CHOH-CHOH-CH2OH

0,1, and 2 were not the right answers..i already tried them! i only have one last try!

Answer 1

In order to be optically active (and have optical isomers) you need to have carbon atoms with 4 different substituents (forming bonds with 4 different groups). Such a carbon atom is a chiral center.
You have 2 optical isomers for each chiral center, the L- and D- or R- and S- depending on which nomenclature you use, one being the mirror image of the other.
In your case you have 2 chiral centers so in total you have 4 optical isomers.

CH2OH-C=O-CHOH-CHOH-CH2OH

The first and last carbon atoms have 2 same substituents (H) so they are not chiral. The second carbon atom as well (the double bond is equivalent to two same substituents). C3 has the sbustituents: -H, -OH, -C(O)-CH2OH and -CHOH-CH2OH which are all different to each other, therefore C3 is chiral.
Similarly C4 is also chiral.

Answer 2

2

Answer 3

If there is a ciral carbon.

The term chiral is used to describe an object which is non-superimposable on its mirror image. In terms of chemistry, these objects are usually molecules and the study of chiral molecules and associated phenomena is a very active area.

A molecule is chiral when it cannot be superimposed on its mirror image (see diagram) with the two mirror image forms referred to as enantiomers. A mixture of equal amounts of the two enantiomers is said to be a racemic mixture. Chirality is of interest because of its application to stereochemistry in inorganic chemistry, organic chemistry, physical chemistry and biochemistry. The study of chirality falls in the domain of stereochemistry.

The term non-superimposable distinguishes mirror images which are superimposable, such as the letter "A" and its mirror image, from those that are not. The classic example of this are human hands. The left hand is a non-superposable mirror image of the right hand: No matter how the two hands are oriented relative to one another, one cannot line up all the major features of one hand with the other, whereas such an operation is trivial for a non-chiral mirror image (e.g., the letter "A").

The two "hands" (enantiomers) of a chiral molecule are sometimes referred to as optical isomers.

Answer 4

2butene can be cis or trans because of the 2 different position of H(on the same or in different planes). the C 2 of 2 hyroxybutanoic acid( or alpha hidroxybutirric acid) is chiral( I'm Italian, I don't know the translation in English) , so it has 4 different groups linked( COOH, H, OH and CH2-CH3) thus the acid can be D or L if you use Fish projections based on "glyceraldeyde"( sorry for problems in translation) .speaking of optical matter it can be + or - depending on where the polarized light moves.. I hope having been clear