Chapter 2: Isomers Flashcards

1
Q

what are structural isomers

A

share only the molecular formula; different chemical and physical properties

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2
Q

what are conformational isomers

A

differ by rotation around sigma bond

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3
Q

what are staggered conformations

A

60 degrees apart

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4
Q

what are anti staggered conformations

A

two largest groups 180 degrees apart; strain minimized

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5
Q

what are gauche conformations

A

two largest groups 60 degrees apart

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6
Q

what are eclipsed conformations

A

groups directly in front of each other

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7
Q

what are totally eclipsed conformations

A

two largest groups in front of each other; strain maximized

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8
Q

what is angle strain

A

stretching or compressing angles from their normal size

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9
Q

what is nonbonded strain

A

interactions between substituents attached to non adjacent carbons

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10
Q

what is axial position

A

sticking up or down from plane of molecule; more strain

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11
Q

what is an equatorial position

A

in the plane of the molecule; less strain

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12
Q

what are configuration isomers

A

can only be interchanged by breaking and reforming bonds

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13
Q

what are enantionmers

A

nonsuperimposable mirror images; opposite stereochemistry at every chiral carbon; same chemical and physical properties

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14
Q

what are racemic mixtures

A

equal concentrations of two enantiomers rotations that cancel one another out

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15
Q

what are meso compounds

A

internal plane of symmetry ; optically inactive

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16
Q

what are diastereomers

A

non-mirror images; differ at some but not all chiral centers; different chemical and physical properties

17
Q

what are cis-trans isomers

A

subtype of diastereomer in which groups differ in position about an immovable bond

18
Q

what is relative configuration

A

gives the stereochemistry of a compound in comparison to another

18
Q

what is a chiral center

A

carbon with four DIFFERENT groups attached

18
Q

what is absolute configuration

A

gives stereochemistry without having to compare; uses Cahn-Ingold-Prelog Priority rules

18
Q

what is a Z alkene

A

highest priority substituents on same side of double bond

19
Q

what are the Cahn-Ingold-Prelog Priority rules

A

highest atomic number = highest priority

20
Q

what is an E alkene

A

highest priority groups on opposite sites of double bond

21
Q

how is stereochemistry determined

A

lowest priority group in the back; draw circle from group 1 to 2 to 3; if circle is clockwise (R); If circle is counterclockwise (S)

22
Q

what are the lines in fisher projections

A

vertical –> dashes
horizontal –> wedges