Question

3. Diastereomers and Meso Forms. When a molecule has two or more stereogenic centers, stereoisomers that are not mirror images can exist; these are called diastereoisomers. Within this general class, there are special types of stereoisomers that are always optically inactive and are called meso forms. Construct a model with four different colored balls about a carbon center. Construct another identical to the first and verify this by the superimposition test. Now remove the same colored balls, blue (C from Fig 1) for example, from each model and join the two carbons at the vacant valence sites as shown in Fig 2. BD state Fig 2 How many stereogenic carbons does this model have? Note that each carbon has the same four groups attached to it._d Conformationally adjust (by rotation about the central C-C bond) the model in a search for symmetry. Does the molecule have a plane of symmetry? Yes_ No Construct the mirror image of this molecule. c. Are the mirror images identical? Yes No d. What term is used to describe the relationship between the two molecules in 3c? R antiomers e. Examine each of these models to determine whether they are chiral or achiral. Interchange two balls (A and B for example as shown in Fig 3) on one carbon of one model. Fig 2 Fig 3

Answer 1

Date Page a No. of stereogenic lo Center On rotation А с Α - - Α No, molecule have no plane of symmetry Mirror images are not identical They are non-superimposable mirror so called Enantiomers. images they e They are are chiral. chiral.

Date Page On Interchane two balls ci so sinin Two models (x) and (y) are not identical No they are not mirror images. Yes. are stereo isomers. Diastereomers. conformation of Medel (x) в D-7 A NOT 1200 D A ΝΟ BB A A o present e No, is on the mirror image of this model neither identical nor nonsuperimposable the original. . " chiral- Yes, fig (3) is optically active i Diastereomer