Question

12. Erythronolide B is the biological precursor of erythromycin, a broad-spel antibiotic. How many chirality centers does erythronolide B have? H-C A CH, нсон CH / O HC H30H ***OH CHE Erythronolide B a. 8 b.9 c. 10 d. 11 13. Consider the two methyl groups indicated with letters in the following molecular model. These two groups are: a. A: axial B: axial b. A: axial B: equatorial c. A: equatorial B: axiald. A: equatorial B: equatorial 14. Which of the following can exist as cis-trans isomers? a. cyclohexane b. methylcyclohexane c. 1,1-dimethylcyclohexane d. 1,2-dimethylcyclohexane

Answer 1

chirality is a property of a chiral, molecule which is non super impossiable on it's mirron image.no Generally gf a Carbon atom has 4. different groups then it is considered as the chiral centre. brood out он Chiral Carbon contre - COOH CH3 A OH CH3. DOO COOH H This carbon is also a Chiral carbon. If the two atoms are in same connectivity then we should go to the next carbon and if there is a different connectivity then the carson Centre is considered as chiral. Here the has the are lies chiral carbon centre has two different groups which in blane. If we go from

the central carbon then there is two CH2 groups, same but thereafter the connectivity d different, one is OH group and another į cool. So, the molecule is chiral. The compound given here ģ - Outs T OM 2014 Here all the carbon centres except C-1, (-7, c-q, C-14 . and (-15 are Chiral. Total Chiral Carlon= 10. C-l and c-a are spe planner Carbon, no for four different groups, so no chirality c-14, c-7 has 2 H atoms, same group so no chirality. C-15 ý also not Chiral. suppose that c-3, the next two carlon atoms de c-4 and c-2 Loth

Contain -CH₂ group, same groups but next to that carbon atoms ie cal and c-5 there iu co group and -OH group attached. So, different groups so, Chiral. so the chiral centres are - ex c-2, 6-3 c-4,2-5, C-6, 6-8, e-10 C-ll, C-12, C-13 Total = 10 : Option e) ý correct.