Test 3 Flashcards
sigma is an
internal plane of symmetry
define chiral
a carbon atom bonded to 4 DIFFERENT unique groups
can atoms with double or triple bonds be chiral
NO
chiral is to
directionality
how do sigmas impact chirality
molecules with sigmas do NOT have chirality
geminal
two functional groups bonded to the same carbon
can a molecule be achiral but have chiral atoms
YES
how to determine chiral atom on cyclic compounds
starting at carbon in question, move clockwise and then counterclockwise around the cyclic compound.
if you encounter the same pattern in both directions there is an internal plane of symmetry and it is ACHIRAL.
if the pattern is different, there is no internal plane of symmetry and it is CHIRAL.
how to rank priority of atoms when determining directionality
higher atomic number = higher priority
impact of the priority 4 atom
NOT NECESSARY for determining R or S configuration
priority 4 atom should be on a HASH
the ________ the unbranched chain, the more important it is
LONGER
tiebreaker protocol for same atoms when chains are UNBRANCHED
whichever atom is part of a longer (unbranched) chain is more important
tiebreaker for chains when one or more is branched
add up protons of atoms directly connected to atom in question
H should be on a
hash
enantiomer
mirror image
enantiomer of an R molecule is
S
in order to draw an enantiomer there MUST be
at least one chiral carbon
2 methods of drawing enantiomers
1) flip all wedges and hashes
2) draw mirror image
ring flip method
left <-> right
wedge <-> hash
diastereomers
non-superimposable
not mirror images
meso compound
molecule has multiple chiral carbons but is NOT a chiral molecule
D =
right handed
L =
left handed
the d,l pattern is
dextro, levo
2 chiral, no sigma
SS or RR
the meso pattern is
internal mirror plane
2 chiral, 1 sigma
SR, RS
chiral atoms are ______ active
optically
2S, 3R-dibromobutane diastereomers
2R, 3R or 2S, 3S
2S, 3R-dibromobutane enantiomer
2R, 3S
R ring flip ->
R
R mirror image ->
S
R draw the enantiomer ->
S
R Td rotation pinwheel ->
R
are diastereomers or enantiomers more difficult to separate, why?
enantiomers
same boiling point, same polarity, etc
Dextro- stands for ______. Dextro- is otherwise stated as ____. It refers to a molecule which _____________.
dextro-rota-tory
+
rotates light clockwise
Levo- stands for ______. Levo- is otherwise stated as ____. It refers to a molecule which _____________.
rotates light counterclockwise
drawing meso compounds
descending/ascending staircase format
wedge/wedge or hash/hash
drawing d,l compounds
descending/ascending staircase format
wedge/hash or hash/wedge
tetrahedral rotations
spin bottom 3
think pinwheel on stick
how does a ring flip impact wedges and hashes
inverts them
