Nomenclature 3 Flashcards

1
Q

IUPAC Rules for assigning configuration at a tetrahedral stereocenter: #1

A

1: Assign priortities 1-4, with 1 being the highest, to each of the four substituents bonded to the stereocenter

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2
Q

IUPAC Rules for assigning configuration at a tetrahedral stereocenter: #2

A

orient the molecule so that the lowest priority substituent is pointed AWAY from you

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3
Q

IUPAC Rules for assigning configuration at a tetrahedral stereocenter: #3

A

Designate R or S:

R: priority 1,2,3 substituents are arranged CLOCKWISE

S: priority 1,2,3 substituents are arranged COUNTERCLOCKWISE

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4
Q

Cahn-Ingold-Prelog Priority Rule #1

A
  1. If the atom’s at the substituent’s points of attachment are DIFFERENT:
    a) atom with higher atomic number has priority
    b) atoms have the same atomic number but are isotopes, the heavier isotope has priority
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5
Q

Cahn-Ingold-Prelog Priority Rule #2

A

if atoms at point of attachment are identical, then priorities of the substituents are set one bond away, following rule 1

a) compare each set’s highest priority atom - if different, atom with highest priority corresponds to substituent with higher priority substituent
b) if highest priority atoms are identical, compare each set’s second-highest priority atom to break tie
c) if second-highest priority atoms in the two sets are identical, then compare each set’s lowest priority atom to break the tie

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6
Q

Cahn-Ingold-Prelog Priority Rule #3

A

If sets of atoms 1 bond away from the point of attachment are identical, then rule 2 is applied to sets of atoms 1 additional bond away from the point of attachment. Continue to move further away until there is a difference.

a) if substituent’s backbone is branched, then follow the chain on which the higher-priority atoms come first
b) if the 2 atoms being compared are the same and one of them is a terminal atom, then the substituent to which it belongs has the lower priority
c) if a point of difference is never encountered, then the substituents must be identical

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7
Q

If atoms x & y in a substituent are connected by a double bond, then we treat x as being ________ and y as being ___________.

A

singly bonded to two y atoms and y as being singly bonded to two x atoms

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8
Q

If atoms x & y in a substituent are connected by a triple bond, then we treat x as being ________ and y as being ___________.

A

x as being singly bonded to 3 y atoms and y as being singly bonded to 3 x atoms

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9
Q

If multiple stereocenters exist in a molecule:

A

each stereocenter receives its own (R) or (S) designation

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10
Q

When naming multiple stereocenters the designation appears:

A

before any number that identifies the location of a substituent on the corresponding stereocenter (R) or (S)

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11
Q

Vertical bonds in a Fischer projection point _______ you and horizontal bonds point __________ you.

A

away from, toward

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12
Q

In a Fischer projection, the proper orientation of the lowest priority group is:

A

a vertical bond, up or down doesn’t matter

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13
Q

If two molecules are related by the inversion of some, but not all tetrahedral stereocenters, they are:

A

diastereomers

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14
Q

If two molecules are related by the inversion of all tetrahedral stereocenters, they are:

A

enantiomers

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15
Q

Protocol for assigning E/Z:

A

determine which of the two substituents on each alkene has the higher priority

if the 2 higher priority groups are on the ZAME ZIDE: assign Z

If the two higher priority groups are on EITHER side: assign E

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16
Q

A double bond that is part of a ring can have both Z and E configurations. Which is less stable and why?

A

For rings with 7 or fewer carbons, E is unstable due to significant ring strain.

17
Q
A