arrangement flexible by free rotation about a single bond
Permanent geometry (bonding)
molecules with the same connectivity&formula but diff 3D arrangement
non-superimposable mirror images
, differ in configuration at ALL C*
Stereoisomers that are not mirror images, differ in configuration in at least 1 C* but not all
Racemic mixture / Racemate
has equal amounts of both enantiomers of a molecule
Priority is clockwise
Priority is counterclockwise
sp3 bond angle (º)
sp2 bond angle (º)
sp bond angle (º)
sp3 C-C bond length (Å)
sp2 C-C bond length (Å)
sp C-C bond length (Å)
sp3 C-H bond length (Å)
sp2 C-H bond length (Å)
sp C-H bond length (Å)
a carbon with 4 DIFFERENT constituents
Which stereoisomer can be isolated at Room Temp?
Configurational Isomers. Conversion usually involves breaking a bond (>80 kJ/mol)
Which stereoisomer is NOT isolatable at room temp?
conformational isomers. involves twisting or inversion. (<80 kJ/mol)
Impossible symmetry combination
Cn, n sigma v, i
Symmetry elements of a C1 point group?
Symmetry elements of a Cn point group?
only 1 axis (n= order of axis)
Characteristics of a C point group?
only 1 symmetry axis (excluding C1, Cs & Ci)
Characteristics of a D point group?
nC2 axes perpendicular to the principal axis
Symmetry elements of a Ci/S2 point group?
i (inversion center) only
Symmetry elements of a Cs point group?
Symmetry elements of a Cnh point group?
Cn, σh, [i]. if n is even, has i. if odd, no i.
Symmetry elements of a Cnv point group?
Cn, n σv
What is conical symmetry?
Symmetry elements of a Dnh point group?
Cn, n C2 ⊥ to Cn, n σv, σh, [i: if n is even]
What is cylindrical symmetry?
Symmetry elements of a Dnd point group?
Cn, n C2 ⊥ to Cn, n σd, [i if n is odd]
What is σd?
σv that don't contain C2 axes but bisect the angle formed by the C2 axes.
Point group possibilities for a linear molecule
C∞v or D∞H
What is crypto-chirality?
Chirality is hidden when differing substituents is far from the asymmetric C
D configuration for sugars (OH defining)
CHO being on top of fischer projection, OH is on the right of the last asymmetric carbon
L configuration for sugars (OH defining)
CHO being on top of fischer projection, OH is on the left of the last asymmetric carbon
L configuration for amino acids (NH2 defining)
COOH being on top of fischer projection, NH2 is on the left of the first asymmetric carbon
Priority of a lone pair?
Lower than H
Pseudo-asymmetric carbon/Stereogenic center
a carbon with 2 similar constitutions but they differ in configuration
Pseudo-asymmetric carbon/stereogenic center notation
Assign priority (R>S), and write r or s (LOWERCASE!)
Number of stereoisomers for a molecule
for n C*, 2^n stereoisomers exist (less for a meso compound)
differ in configuration at ONLY one C*
What is molecular chirality?
Molecules that are chiral withouh having a C*
Inversion of configuration through twisting
Axial chirality configuration assignment (aR, aS)
Planar chirality configuration assignment (pR, pS)
handle on top, pilot atom (1st oop atom of higher priority), follow through according to priority (abc). Right turn=pR. Left turn=pS
Helical chirality configuration assignment (P,M)
View like a screw, clockwise=P, counterclockwise=M
Which point groups (3) contain chiral molecules
C1, Cn, Dn
A meso-compound consists of...
A sigma in eclipsed conformation, otherwise i
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