Stereochemistry and Isomerism (3) - conformation

Question 1

different spatial arrangement

Answer 1

rotation around bonding

Question 2

how conformation is made

Answer 2

made different by rotation of chemical bonds

Question 3

staggered conformation

Answer 3

substituent located far from each other

Question 4

eclipse conformation

Answer 4

substituents located in the same plane

Question 5

stability of stagger vs eclipse

Answer 5

staggered - more stable - chemical bonds one from each other

due to chemical bonds - compose of e- - repel

Question 6

Newman molecules projection - view

Answer 6

along axis of bond - placing circle in middle and perpendicular to bond and project molecule

Question 7

example - Newman molecules projection - ethanol

Answer 7

determine from RHS

projected easily - allow derivation of dihedral angle

Question 8

dihedral angle

Answer 8

angle between 2 bonds of substituent on adjacent atom

Question 9

cyclohexane

Answer 9

not flat ring - in order have 109 degree 28’ bond angles

Question 10

chair conformation example

Answer 10

diamond lattice - form chair cyclohexane building block

Question 11

2 types of substiuents

Answer 11

axial - perpendicular to plane

equatorial - along the plane

Question 12

rotation in cyclohexane - ring inversion

Answer 12

moves one side of plane up - forming boat formation

move other side of plane down

Question 13

ring inversion

Answer 13

axial substituent become equatorial - vice versa

v. dynamic

Question 14

monosubstituted cyclohexane

Answer 14

thermodynamic preference for equatorial substituted chair

- H atoms - v. close - repel

Question 15

chair formation stability vs boat formation

Answer 15

chair formation - more stable - all the bonds are staggered

Question 16

carbohydrates - naturally occurring

Answer 16

D-sugars - absolute configuration of stereogenic centre at bottom of fisher
L-sugar - L-fucose

Question 17

chemically not most stable molecule

Answer 17

hemi-acetal = one alcohol react to aldehyde

conversion from fisher structure to cycle structure straightforward

Question 18

sawhorse to chair form

Answer 18

in C1 - OH is above the plane therefore will be at equatorial
C2 on the equatorial - below axial - below plane