stereoisomerism (2)

Question 1

enantiomers

Answer 1

pair of isomers - mirror images are not superimposable

molecules have chirality

Question 2

example - ethanol

Answer 2

mirror able to rotate and is same as original therefore not enantiomers
and are achiral

Question 3

example - lactic acid

Answer 3

rotate 180 - different to original as OH is above the plane while original is OH is below the plane
enantiomer - mirror image is not superimposable - chiral

Question 4

example - erythrose

Answer 4

mirror image differ - enantiomer

chiral but have 2 stereogenic centres on both - opposite chirality in mirror image

Question 5

chiral

Answer 5

not superimposable with mirror images

can derive from other sources and doesn’t always contain stereogenic centres

Question 6

optical rotation

Answer 6

all physical properties of enantiomers are identical except optical rotation

Question 7

chiral molecules in optical rotation

Answer 7

plane polarised light pass through solution and remains

Question 8

achiral molecules in optical rotation

Answer 8

plane polarised light pass through solution - rotation in light

Question 9

angle of rotation in polarimeter

Answer 9

angle alpha depend on concentration of solution (c), path length (l) and specific rotation [a] - characteristics of molecules

Question 10

equation of characteristics of molecules

Answer 10

a = [a].D.c.l

temperature and wavelength dependent

Question 11

racemic mixture

Answer 11

1:1 mixture of enantiomers

Question 12

enantioenriched

Answer 12

ratio not 1:1 mixture

Question 13

enantiopure/homochirality

Answer 13

no other enantiomer

Question 14

Diastereomers

Answer 14

pair of stereoisomers - don’t bear mirror images relation

Question 15

examples of diastereomers

Answer 15

threose and erythrose
glucose and galactose
they have same constitution but different arrangement of atoms and not mirror image

Question 16

having >1 stereogenic centre in diastereomers

Answer 16

need at least one stereogenic centre that is different

Question 17

epimer

Answer 17

diastereomer where only one out of some stereogenic centre is different

Question 18

example of epimer

Answer 18

glucose and galactose - 5 SC and 1 is different

Question 19

example of each diastereomer having corresponding enantiomer

Answer 19

D-erythrose and L-erythrose

Question 20

mesoform

Answer 20

structure has SC but are achiral

Question 21

example of mesoform - 2-tartaric acid diastereomer

Answer 21

rotate 180 horizontally and will be same

superimposable but one chiral and other is achiral

Question 22

geometric isomers

Answer 22

stable entities and can’t easily interconvert

compounds with different chemical and physical properties

Question 23

geometric isomers in alkene

Answer 23

focus on relative positions of substituents of C=C - cis/trans (same or opposite side horizontally respectively)

Question 24

geometric isomer in ring structure

Answer 24

cis and trans - same and opposite side of ring plane

used to describe different substituent - 2 different on same side - cis

Question 25

Fischer representation

Answer 25

uses horizontal and vertical lines | using highest priority at apical position located at top end

Question 26

horizontal lines in fischer

Answer 26

located in front of plane

Question 27

vertical lines in fischer

Answer 27

located behind plane - carbon chain

Question 28

relation of sawhorse and fischer

Answer 28

substituent located on same side in Fischer = different sides in sawhorse

Question 29

which representation used for carbohydrates and amino acids

Answer 29

Fischer representation

Question 30

CIP nomenclature used:

Answer 30

alkene geometric isomer - E/Z | SC(differentiate enantiomers/diastereomer - R/S

Question 31

CIP

Answer 31

Catin Ingold Prelog absolute configuration differentiated by unambiguous nomenclature

Question 32

How CIP nomenclature works

Answer 32

- identify substituent C=C or SC - assign priority sequence based on atomic mass - from priority assign E/Z or R/S

Question 33

E

Answer 33

entgergen - across

Question 34

Z

Answer 34

zusammen - together

Question 35

Nomenclature in SC - process

Answer 35

- see 4 atoms directly bonded to SC - priority sequence based on atomic mass - assign R/S - by placing lowest priority at back of plane and go from highest to lowest to see if it is going clockwise (R) or anticlockwise (S)

Question 36

if 2 atoms are identical when looking at the nomenclature

Answer 36

look at next atom - what they are bonded to

Question 37

atoms with double or triple bonds in Nomenclature

Answer 37

given single bond equivalences

Question 38

phantom atom

Answer 38

new carbon representing double of triple bonds

Question 39

when having 2 SC

Answer 39

2 enantiomers having S,S and R,R

Question 40

R,R and R,S | S,R and S,S

Answer 40

diastereomer pair of compounds - determining absolute configuration of SC - compare molecules and see if they're enantiomers/diastereomer/ just equal to each other

Question 41

example of 2SC in 2 enantiomers

Answer 41

L/D-erythrose and L/D-threose

Question 42

why this is important

Answer 42

most biological isomers - amino acids, nucleic acids, FA, cholesterol to proteins and other polymers increase in complexity

Question 43

example of important biological isomer

Answer 43

thalidomide - R - nausea-treatment but S- cause birth defects

Question 44

absolute configuration

Answer 44

spatial arrangement of atoms of chiral molecule