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1101 > Chirality > Flashcards

Chirality Flashcards

1
Q

STEREOISOMERS

A

Different SPATIAL ARRANGEMENT of atoms

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2
Q

CONSTITUTIONAL ISOMERS

A

Different CONNECTIVITY of atoms.

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3
Q

ENANTIOMERS

A

stereoisomers: non-superimposable mirror images

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4
Q

DIASTEREOMERS

A

stereoisomers: non-superimposable, not mirror images

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5
Q

State main features of GEOMETRIC isomers

A

Z / CIS: SAME FACE
E / TRANS: OPPOSITE FACES

NO interconversion at body temp.

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6
Q

CIP rules

A

Z- (priority 1 on SAME FACE of alkene)
E- (OPPOSITE FACE)

ASSIGN HIGHEST PRIORITY ATOMS

CLOCKWISE - R
ANTICLOCKWISE -S

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7
Q

STEREOISOMERS are not interconvertable.

T or F?

A

T

ASYMMETRIC CENTRE

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8
Q

OPTICALLY INACTIVE

A

ACHIRAL MOLECULES or RACEMIC MIXTURE

No net rotation of PPL

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9
Q

RACEMIC MIXTURE

A

1:1 MIXTURE OF ENANTIOMERS

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10
Q

CHIRALITY

A

NON-SUPERIMPOSABLE

ASYMMETRIC centre

Saturated C w 4 different groups

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11
Q

ACHIRAL

A

SUPERIMPOSABLE

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12
Q

ENANTIOMER

A

CHIRAL
NON-SUPERIMPOSABLE
MIRROR IMAGE

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13
Q

DIASTEREOMERS

A

NON-SUPERIMPOSABLE, NON-MIRROR images

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14
Q

Compare enantiomers & diastereomers

A

ENANTIOMERS have IDENTICAL physical & chemical properties

DIASTEREOMERS have DIFFERENT physical properties

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15
Q

ERYTHRO vs THREO enantiomers

A

ERYTHRO: H on SAME SIDE of chain
THREO: H on OPPOSITE SIDES

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16
Q

MESO compounds

A

ACHIRAL compound with CHIRAL centres
Internal plane of symmetry - SUPERIMPOSABLE MIRROR
OPTICALLY INACTIVE

17
Q

R enantiomers

A

Rotate PPL CLOCKWISE

(+) enantiomers

18
Q

S enantiomers

A

Rotate PPL ANTI-CLOCKWSIE

(-) enantiomers

19
Q

ENANTIOMERS have _____ physicochemical properties. EXCEPT:

A

IDENTICAL

EXCEPT:
ROTATION OF PPL
INTERACTION WITH OTHER CHIRAL MOLECULES

20
Q

How do ENANTIOMERS rotate PPL ?

A

OPPOSITE DIRECTIONS
by EQUAL AMOUNTS - racemate
unless enantiomerically favoured

21
Q

ROTATION OF PPL BY ENANTIOMERS

  • DEXTROROTATORY
  • LEVOROTATORY
A

(+) CLOCKWISE, d

(-) ANTICLOCKWISE, l

22
Q

ENANTIOMERIC EXCESS

A

Amount of pure enantiomer in XS of racemic mixture

23
Q

FISCHER PROJECTIONS

A 
HORIZONTAL bonds (WEDGE) protrude (out of plane)
VERTICAL bonds (DASH) into plane
24
Q

MESO compounds

A

have an INTERNAL PLANE OF SYMMETRY

ACHIRAL compounds, with CHIRAL centres

SUPERIMPOSABLE

OPTICALLY INACTIVE

25
Q

2^n shows

A

maximum possible stereoisomers

n = number of chiral centres

26
Q

Chiral compounds cannot have a plane of symmetry? T or F

A

T

27
Q

Separation of DIASTEREOMERS:

A

DIFFERENT SOLUBILITY in SOLVENTS

- CRYSTALLISATION

28
Q

Separation of ENANTIOMERS:

A

RESOLUTION: from racemic or enantiomerically enriched mixture by CRYSTALLISATION

CHIRAL CHROMATOGRAPHY

29
Q

Describe RESOLUTION for separation of diastereoisomers

A

DIFFERENT SOLUBILITIES of diastereoisomeric salts allow for:

CRYSTALLISATION of 1 diastereomer, evaporation of other
RECOVERY of enantiomers by ACIDIFYING separated diastereoisomeric salts.

30
Q

Describe RESOLUTION by ESTERIFICATION

A

Covalent bond forms between chiral carboxylic acid & alcohol.

Separate diastereomers by CRYSTALLISATION then RECOVER enantiomers by ESTER HYDROLYSIS.

31
Q

Why can diastereoisomers be separated?

A

On basis of DIFFERENT SOLUBILITIES.

32
Q

STEREOSELECTIVE reaction

A

PREFERENTIAL formation of one stereoisomer.

33
Q

STEREOSPECIFIC reaction

A

each stereoisomeric reactant produces a different stereoisomeric product or different mixture of products

34
Q

NO STEREOSELECTIVITY results in

A

RACEMIC MIXTURE

35
Q

CONCERTED REACTION

A

bond breaking & making occurs in SAME STEP

E.g. SN2, E2

INVERTED or CONSERVED stereochemistry

36
Q

NON-CONCERTED reaction

A

Bond breaking & making in DIFFERENT STEPS.

INTERMEDIATES formed - allow changes to stereochemistry

E.g. SN1, E1

RACEMISATION occurs if intermediate forms

37
Q

State 3 types of constitutional isomers.

A

FUNCTIONAL, POSITION, SKELETAL (chain)

38
Q

State 2 categories & subtypes of STEREOISOMERS

A

GEOMETRIC

Molecules with chiral centres: ENANTIOMERS & DIASTEREOMERS

1101 (8 decks)

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