Question

7. (9 pts) (Are the following optically active or meso? meso HyCHC OH HO opticaly actve active opti call active 8. (3 pts) How many stereoisomers are there of 2,3-dibromobutane? 4 sleeoisamvers (8 pts) Circle the letter of the statements that are true. a. Racemic mixtures are optically active Enantiomers have specific rotations that are equal, but have opposite signs 9. o adtc) Achiral molecules are optically inactive d Meso compounds contain equal amounts of enantiomers

Answer 1

H11 KI/ since, it Plane of HC is a chixal molecule. There will be a symmetry. Hence it is optically active OH OH It is also active Br C#, CHy is a chiral- molecule. So, it is optically BO B Yes, it is a meso compound The cyclohexane molecule exists as two conformers the chair form and the boatform. The chair form doesn't have a plane of symmetry thus it isn't a meso compound, it is a chiral However the boat form does have a plane of Symmetry, even with the boomine attached on. the same side Cois). Thus the molecule is a meso compound. not chiral as Bobromo Cis-1-3-dimethyl cyclohexane is it has a plane of symmetry trans 1-3-di bromo cyclo hexane is is optically active. chiral. so it.

, since e no CH₂ a) The molecule 23-dibsomo butane has 2 Chical centas The maximum number of stered isomers is an. where nis number of chical centres since n=2, the maximum no of stereoisomess is 22=4. CHCH # B0 80H H BO 88+ Bo LH 1-88 H B Br LH # CH3 CH CHA u structures and 2 are two different nonsuperimposable missor images of each other. But Stouctures 3andų are meso compounds. as they are superimposable on each other, so they are the same compound y so there are only three stereoisomess of 2,3-diborimo butane 9. a) Racemic mixtures are optically active This is a false statement. This is due to the fact that in equimolecular mixture of enantiomeric Pairs, the sotation caused by the molecules of one. enantiomes is cancelled by the sotation caused by the molecules of other enantiomer. 1) Enantiomes o have specific rotations that are equal, but have opposite signs This is a true statement Enantiomes have equal and Opposite specific sotations, which is why enantiomers are also sometimes called "optical isomers". A solution containing equal amounts of two enantiomers is Known as racemic mixture

C) Achiral molecules are optically inactive. This is a true statement in a chiral solution. that is not a racemic lucture, however the chiral molecules present in greater numbers are configuration -ally equivalent to each other, and therefore each possesses identical electoon Clouds to its moecular twins (d) Meso compounds contain equal amount of enantiomers. This is a false statement. Meso compounds are loptically inactive due to these differing absolute. configurations on the opposing setreocenters- A meso Compound is achiral so cannot have an enantiomes When a molecule is superimposable on its missor image, then that molecule and the mirror image are merely the same molecule. Fisher projection of (s)-2-methyl-3-bromo- hexane. HH HN 1 CH₂ C C -C- CH3.. CH BV