Question

Which of the following is written correctly? A. Fisher projections are typically drawn with hydrogens on vertical lines and carbon chains on horizontal lines. B. In the case of a tie, atom priorities are assigned based on the functional groups attached to the next atom in the chain C. When choosing between R and S the highest priority atom should be pointing atom should be pointing toward the viewer. D. Rotation around C = C is typically hindered because of sigma bond overlap E. When numbering carbons in a chain, choose the order that assigns the highest possible numbers to all functional groups Threonine, pictured at right, is an essential amino acid. What are the configurations of each stereocenter in this molecule? A. This compound is meso B. (2S, 3S) C. (2R, 3S) D. (2R, 3R) E. (2R, 3S) Refluxing allows for: A. Gentler reaction conditions B. Chiral synthesis C. Removal of impurities D. Increased reaction temperatures with little solvent loss E. Increased reaction temperatures with little sample loss When converting maleic to fumaric acid, what is the purpose of adding hydrochloric acid? A. Protonates the C = O, allowing for molecular rotation B. Protonates one of the C = C carbons, resulting in breakage of the Product-bond C. Protonates the hydroxyl group allowing for elimination of water D. Causes the maleic acid to be more soluble in water. E. Has no real effect

Answer 1

12.

Answer: A. Fischer projections are typically drawn with hydrogens on vertical lines & carbon chains on horizontal lines

In case of tie the atom priorities are assigned based on the molecular weight of the next atom in the chain, therfore B is not correct

In choosing between R & S, The lowest priority group should be away from the observer.

Rotation of C=C bond is hindered by the Pi bond overlap

when numbering carbons in a chain, Choose the order that assigns the lowest possible number to the functional groups

13.

14.

D. Increased reaction temperatures with little solvent loss

refluxing allows the reaction to be heated at the boiling temeratures of the solvent with the vapours getting condensed back to the reaction medium.

15.

A. Protonates the C=O, allowing for molecular rotation.

The protonation of the carbonyl oxygen increases the electrophilicity of the carbonyl carbon polarising the C=C double bond which is in resonance with the C=O bond, Allowing for the molecular rotation to convert maleic acid to fumaric acid.