C8. Configurational stereoisomers

Question 1

all carbons in cyclohexane are…

Answer 1

sp3 hybridised

Question 2

all carbons in benzene are…

Answer 2

sp2 hybridised

Question 3

Describe geometric isomerism

Answer 3

restricted rotation about double bond leading to cis and trans isomerism

Question 4

Describe the Cahn-Ingold-Prelog Priority rules

Answer 4

-Higher atomic number precedes lower
-For isotopes, higher atomic mass precedes lower
-If atoms have the same priority, secondary atoms attached are considered
-For the purpose of determining priority, double and triple bonds are
treated by assuming each atom is duplicated or triplicated (one note for more detail)

Question 5

Z?

Answer 5

high priority on same side

Question 6

E?

Answer 6

high priority on different sides

Question 7

how does a stereogenic centre/ chiral centre arise?

Answer 7

Four different groups on
tetrahedral carbon

Question 8

what is a an enantiomer?

Answer 8

The two molecules with opposite
configurations are called
enantiomers. One chiral centre > two possible enantiomers. They are chemically identical except in optical properties and sometimes biological properties.

Question 9

how to locate a stereogenic centre? (one note)

Answer 9

-Generally, a stereogenic carbon is sp3
-Four different groups are attached to the carbon

Question 10

how do you use the Cahn-Ingold-Prelog System to describe configuration at stereogenic centres? (one note for diagram example)

Answer 10

a) Assign an order of priority to substituents on stereogenic centre
b)View the molecule from the side opposite the group of
lowest priority
c) If the order of decreasing priority of the remaining groups gives a
clockwise sequence, the configuration is
R (rectus); if the sequence
is anticlockwise, the configuration is
S (sinister)

Question 11

configuration?

Answer 11

spatial sequence about stereogenic centre

Question 12

what is optical activity?

Answer 12

ability of a compound to rotate the plane of
polarized light; observed in polarimeter. Enantiomers rotate the plan in opposite direction

Question 13

eutomer definition?

Answer 13

the enantiomer of a chiral compound that has a higher pharmacological activity or is more potent for a specific action

Question 14

distomer definition?

Answer 14

the enantiomer of a chiral compound that is less potent than the eutomer for a specific action

Question 15

Describe salbutamol

Answer 15

-Salbutamol is a short-acting, selective
2-adrenergic receptor agonist
-It is 29 times more selective for B2 receptors than B1 receptors giving it higher
specificity for pulmonary B2 receptors versus B1 receptors located in the heart.
-Salbutamol is formulated as a racemic mixture of the R- and S-isomers.
-The R-isomer has 150 times greater affinity for the beta 2-receptor than the Sisomer. However the enantiomerically pure version of the drug is too expensive.