CBI3 - Biomolecular Bonding

Question 1

Define structural isomers.

Answer 1

Molecules with the same molecule formulas but different structural arrangement of atoms.

Question 2

Define stereoisomers.

Answer 2

Molecules with same structural formula but different spatial arrangement of atoms in a molecule.

Question 3

Which functional group exhibits E-Z isomerism.

Answer 3

Observed in C=C bonds.

Question 4

Define stereocentres.

Answer 4

Geometric points in space where switching the groups give rise to another stereoisomers. Common example is chiral carbon centre with four different attachments.

Question 5

How many configurations does a molecule with n stereocentres have.

Answer 5

2^n number of configurations.

Question 6

Difference between absolute and relative configuration.

Answer 6

Absolute configuration - spatial arrangement of the stereocentres a molecule contains. Relative configuration - spatial arrangement of stereocentres relative to one another.

Question 7

What do enantiomers do to plane polarised light.

Answer 7

Each enanotimer of the same molecule will rotate the plane of polarised light in opposing directions (clockwise or anti-clockwise).

Question 8

Define enantiopure and racemate.

Answer 8

Enantiopure - pure sample of only one type of enantiomer. Racemate - 50:50 mix of both types of enantiomer.

Question 9

Two methods for stereo chemical nomenclature.

Answer 9

CIP rules or CORN rule.

Question 10

When is CORN rule used.

Answer 10

For amino acids.

Question 11

Acronym used for CORN rule.

Answer 11

CDAL.

Question 12

Acronym used for CIP rules.

Answer 12

CRAS.

Question 13

How is priority assigned in CIP nomenclature.

Answer 13

Priority is assigned based on highest atomic number. Groups are ranked from highest priority to low priority.

Question 14

Define diastereomers.

Answer 14

Stereoisomers that differ in one or more but not all of the stereocentres.

Question 15

Define epimers.

Answer 15

Diastereomers that differ in absolute configuration in only one of the stereocentres.

Question 16

Define salt bridges.

Answer 16

Electrostatic forces of attraction/ionic interactions between opposite charges in proteins.

Question 17

Define dipoles.

Answer 17

Uneven distribution of electron cloud leading to polarity on atoms.

Question 18

Which geometrical shapes can lead to non polar molecules.

Answer 18

Linear, trigonal planar, tetrahedral.

Question 19

Name two other types of non-covalent interactions.

Answer 19

Hydrophobic interactions and steric interactions.

Question 20

How do hydrogen bonds form.

Answer 20

Positive charge on hydrogen forms bond with lone pair of electronegative atom. Electronegative atOJ’s are confined to nitrogen, oxygen and fluorine.

Question 21

Do structural isomers have different chemical properties.

Answer 21

If they have different functional groups, will have differing chemical properties.

Question 22

Which amino acid does not exhibit optical isomerism and why.

Answer 22

Glycine - R side chain is H therefore C has two Hs attached.

Question 23

Why do alkenes show E/Z isomerism.

Answer 23

Contain C=C bond which is planar so has restricted rotation as any rotation would be energetically unfavourable.

Question 24

Do optical isomers have different properties.

Answer 24

No is present in symmetrical environment. Only differ in rotation of plane polarised light.

Question 25

Is R/S notation for absolute or relative configuration.

Answer 25

Absolute.

Question 26

Is cis/trans notation for absolute or relative configuration.

Answer 26

Relative.

Question 27

Define anomer.

Answer 27

When sugars cyclise into rings.

Question 28

Give 4 types of non covalent interactions.

Answer 28

Permanent dipole, London dispersion, ionic interactions and hydrogen bonds.

Question 29

Explain why water has higher boiling point than ammonia.

Answer 29

Contains two long pairs and two H atoms to which hydrogen bonds can form.