Organic structure 1-3

Question 1

Isomers

Answer 1

molecules which possess the same molecular formula (C5H10O)
but are different

Question 2

Constitutional isomers -

Answer 2

molecules which possess the same molecular formula but different
constitutions (connectivities).

Question 3

Stereoisomers -

Answer 3

molecules which possess
the same molecular formula AND the same connectivity

Question 4

Enantiomers -

Answer 4

stereoisomers which are mirror
images of each other

Question 5

Diastereomers

Answer 5

• stereoisomers which are not
  mirror images of each other.

Question 6

Conformations

Answer 6

– different shapes possible
for a single molecule (usually related by
rotations about single bonds).

Question 7

chiral centre –

Answer 7

four different groups on a carbon

Question 8

if Stereoisomers are different molecules this means that…..

Answer 8

they have different properties from each other

Question 9

what leads to the difference in qualities in isomers

Answer 9

they have Different interatomic distances this means different dipole moments, melting points,
boiling points, IR and NMR spectra,
solubilities, chromatographic properties etc.

Question 10

draw Two enantiomers with achiral probe molecule

Question 11

draw Two enantiomers with chiral probe molecule

Question 12

chiral molecules can

Answer 12

can distinguish between enantiomers

Question 13

How do you tell if a molecule is chiral?

Answer 13

-Take mirror image, see if it can be superimposed on original.

• consider symmetry of molecule.

Question 14

does a achiral molecule plane of symmetry?

Answer 14

yes

Question 15

High symmetry →

Answer 15

achiral

Question 16

Low symmetry →

Answer 16

chiral

Question 17

Molecule with a simple axis
of symmetry can be

Answer 17

chiral

Question 18

Molecule with a plane or
centre of symmetry is

Answer 18

achiral

Question 19

Molecule with a simple axis
of symmetry can be

Answer 19

chiral

Question 20

Molecule with a plane or
centre of symmetry is

Answer 20

achiral

Question 21

not all molecules without a plane or centre of symmetry
are chiral. Why?

Answer 21

This is because there are further symmetry elements* which can make a
molecule achiral

Question 22

how to calculate the number of isomers?

Answer 22

2n stereoisomers? Where N is chiral centre number

Question 23

Meso forms

Answer 23

are not optically active, does not have enantiomeric forms, but can have chiral shape