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CM133-1 Organic Chemistry 1 > Chapter 5 Stereochemistry: Chiral Molecules > Flashcards

Chapter 5 Stereochemistry: Chiral Molecules Flashcards

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1
Q

What are the subdivision of isomers?

A

isomers to constitutional isomers and stereoisomers to enantiomers and diastereomers

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2
Q

isomers with the same molecular
formula and same connectivity of atoms but different arrangement of atoms in space

A

Stereoisomers

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3
Q

Different compounds with same molecular formula

A

Stereoisomers

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4
Q

isomers whose atoms have a different connectivity

A

Constitutional isomers

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5
Q

isomers that have the same connectivity but that differ in the same arrangement of their atoms in space

A

stereoisomers

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6
Q

stereoisomers that are non superposable mirror images of each other

A

enantiomers

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7
Q

The ability for an isomers to be placed over another isomers, usually in such a way that both will be visible

A

superposable

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8
Q

Not superposable on its mirror image and can exist as a pair of enantiomers

A

chiral molecules

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9
Q

A chiral molecule and its mirror image

A

Pair of enantiomers

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10
Q

Superposable on its mirror image

A

Achiral molecule

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11
Q

A molecule with a _________ bonded to four different groups will always be chiral

A

single tetrahedral carbon

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12
Q

A molecule with ______________ bonded to four different groups is not always chiral

A

more than one tetrahedral carbon

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13
Q

Switching two groups at the tetrahedral center leads to the ______ in a molecule with one tetrahedral carbon

A

enantiomeric molecule

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14
Q

An atom bearing groups of such nature that an interchange of any two groups will produce a stereoisomer

A

Stereogenic center

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15
Q

Carbons at a tetrahedral stereogenic center are designated with an _________

A

asterisk(*)

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16
Q

The binding specificity of a chiral receptor site for a chiral molecule is usually only favorable in one way

A

The Biological Importance of Chirality

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17
Q

consider this when testing for chirality

A

planes of symmetry

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18
Q

An imaginary plane that bisects a molecule in such a way that the two halves of the molecule are mirror images of each other

A

Plane of symmetry

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19
Q

A molecule with a plane of symmetry cannot be _____

A

chiral

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20
Q

Nomenclature of Enantiomers

A

R,S System

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21
Q

The R,S System is also called

A

Cahn-Ingold-Prelog system

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22
Q

The four groups attached to the stereogenic carbon are assigned priorities from ___________

A

highest to lowest

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23
Q

Priorities are assigned as follows:
1. Atoms directly attached to the _____ are compared
2. Atoms with _______ are given higher priority

A
  1. stereogenic center
  2. higher atomic number
24
Q

If priority cannot be assigned based on directly attached atoms, the _________ of atoms is examined

A

next layer

25
Q

The molecule is rotated to put the lowest priority group at the_____

A

back

26
Q

If the groups descend in priority (a,b then c) in clockwise direction
the enantiomer is ____

A

R

27
Q

If the groups descend in priority in counterclockwise direction the
enantiomer is ____

A

S

28
Q

Groups with double or triple bonds are assigned priorities as if their atoms were ________ or _______

A

duplicated or triplicated

29
Q

_________ have almost all identical physical properties (melting point, boiling point, density)

A

enantiomers

30
Q

An empty sample tube or one containing an achiral molecule will
not rotate the plane-polarized light

A

Specific Rotation

31
Q

The amount the analyzer needs to be turned to permit light through is called ______

A

observed rotation (a)

32
Q

If the analyzer is rotated clockwise the rotation is (+) and the molecule is _________

A

dextrorotatory

33
Q

If the analyzer is rotated counterclockwise the rotation is (-) and the molecule is ________

A

levorotatory

34
Q

what is the formula for specific rotation

A

[a] = a/c*l

35
Q

[a]

A

specific rotation

36
Q

a

A

the observed rotation

37
Q

c

A

concentration of the solution in g/ml

38
Q

l

A

length of the tube in decimeters

39
Q

= A 1:1 mixture of enantiomers
= No net optical rotation
= Often designated as (+)

A

Racemic mixture

40
Q

Often a mixture of enantiomers will be enriched in one enantiomer

A

Enantiomeric Excess

41
Q

formula for %enantiomeric excess

A
  1. % enantiomeric excess = moles of one enantiomer - moles of other enantiomer/ total moles of both enantiomers * 100
  2. % enantiomeric excess* = observed specific rotation/ specific rotation of the pure enantiomer * 100
42
Q

The optical rotation of a sample of 2-butanol is +6.76o. What is the enantiomeric excess? its [a] = +13.52o

A

50%

43
Q

The maximum number of stereoisomers available will
not exceed ____, where n is equal to the number of tetrahedral stereogenic centers

A

2^n

44
Q

achiral despite the presence of
stereogenic centers

A

Meso compound

45
Q

= Not optically active
= Superposable on its mirror image
= Has a plane of symmetry

A

meso compound

46
Q

A 2-dimensional representation of chiral molecules

A

Fischer Projection Formulas

47
Q

______ represent bonds that project behind the plane of the paper

A

vertical lines

48
Q

_________ represent bonds that project out of the plane of
the paper

A

horizontal lines

49
Q

A reaction which takes place in a way that no bonds to the
stereogenic carbon are broken is said to proceed with _______

A

retention of configuration

50
Q

the relationship between
comparable stereogenic centers in two different molecules

A

Relative configuration

51
Q

the actual 3-dimensional orientation of the atoms in a chiral molecule

A

Absolute configuration

52
Q

absolute configuratoon can be determined by ______

A

x-ray crystallography

53
Q

Chiral Molecules that Do Not Possess a Tetrahedral Atom with Four Different Groups

A
  1. atropoisomer 2. allenes
54
Q

conformational isomers that are stable

A

Atropoisomer

55
Q

contain two consecutive double bonds

A

Allenes

CM133-1 Organic Chemistry 1 (6 decks)

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