Question | Answer |
Difference between ordinary light and plane-polarized light | Ordinary light has light waves vibrating in all planes, but Plane-polarized light has light waves vibrating in only parallel planes |
What's an optically active compound? | A compound that rotates the plane of polarized light |
What's a polarimeter? | An instrument that measures the ability of a compound to rotate the plane of plane-polarized light |
What does the magnitude of observed plane-polarized light rotation depend on? | The concentration of the compound, the length of the sample tube, the temperature, the solvent, and the wavelength of the used light |
What's a dextrorotary rotation? | A (+) clockwise rotation of the plane of plane-polarized light |
What's a levorotary rotation? | A (-) counterclockwise rotation of the plane of plane-polarized light |
What's an enantiomer? | A nonsuperposable mirror image |
What does chiral mean? | Two molecules or objects are mirror images but are nonsuperposable on eachother |
What does achiral mean? | A molecule and its mirror image are superposable |
What does it mean if a molecule's superposable? | Molecules are identical and there's no possibility of enantiomerism |
Do achiral or chiral molecules rotate the plane of polarized light? | Chiral molecules |
If a molecule contains an internal mirror plane (a plane of symmetry), is it chiral or achiral? | Achiral |
What's another name for a mirror plane? | A plane of symmetry |
Does a chiral molecule have an internal mirror plane? | No |
If there are four different groups bonded to a carbon molecule, is there a mirror plane? | No |
What is a carbon with four different groups bonded to it called? | A stereocenter or asymmetric carbon |
What are three identical physical and chemical properties of enantiomers? | same melting point and boiling point, same bond length and bond strengths, and the same amount of specific rotation (but in opposite direction) |
Are many drugs chiral or achiral? | Chiral |
How do you name a chiral molecule? | 1) Assign a priority from highest (1) to lowest (4) on each molecule of the stereocenter. 2) Lowest priority molecule faces away from you. 3) Read the next 3 from highest to lowest; Clockwise = R, Counterclockwise = S |
What's a diastereomer? | A molecule with 2 [or more?] stereocenters |
For a molecule with X stereomers, how many stereoisomers are possible? | 2^X |
What's a stereoisomer? | Isomeric molecules that have the same molecular formula and sequence of bonded atoms, but differ only in the 3-D orientations of their atoms in space (so each molecule is bonded to the same molecule, but those molecules might be arranged differently) |
What's a meso compound? | An achiral compound that has two or more stereocenters |
What's a racemic mixture? | An equimolar mixture of two enantiomers |
What is the molar ratio of dextrorotary to levorotary molecules in a racemic mixture? | 1:1 |
Does a racemic mixture exhibit optical activity? If so, explain what this means. | No it does not, so it doesn't rotate the plane of polarized light |
What's a resolution? | When a racemic mixture is separated into its enantiomers |
What's usually used to separate racemic mixtures? | Enzymes |
What does the R enantiomer of thalidomide do? | It's effective against morning sickness, insomnia, & coughs, and acts as a painkiller and tranquilizer |
What does the S enantiomer of thalidomide do? | It's teratogenic |
Are many of the molecules in living systems chiral or achiral? | Chiral |
What is chymotrypsin (ki' mo trip' sin)? | An enzyme in the intestine of animals that catalyzes the digestion of proteins |
What are the two types of isomers, and explain their differences? | Constitutional isomers (same molecular formula but different structure) & stereoisomer (same molecular formula, same attachment to atoms) |
What are the two types of stereoisomers? | Enantiomers and diastereomers |
What are the two types of diastereomers? | Conformational isomers and Geometric isomers |
What are the two types of geometric isomers? | Configurational isomers and cis-trans isomers |