The flashcards below were created by user
DesLee26
on FreezingBlue Flashcards.
-
What does the Fischer projection do?
facilitates comparison of stereoisomers, holding them in their most symmetric conformation and emphasizing any differences in stereochemistry
-
Rotation of Fischer projection around 180 degrees?
- when we rotate a Fischer projection 180 degrees, the vertical (dashed) bonds still end up vertical and the horizontal (wedged) lines still end up horizontal
- it is allowed
-
Rotation of Fischer projection around 90 degrees?
- if rotated ninety degrees, the configuration changes
- the vertical bonds become horizontal and the horizontal bonds become vertical
- the molecule is different
- It is not allowed
-
Aside from not turning it ninety degrees, what else can we not do?
flip them over
-
The final rule for drawing Fischer projections helps to ensure that we do not __. This rule is what?
- rotate the drawing ninety degrees
- that the carbon chain is drawn along the vertical line of the Fischer projection, usually with the IUPAC numbering from top to bottom
-
How to draw mirror of Fischer projections?
interchanging the groups on the horizontal part of the cross reverses left and right while leaving the other directions unchanged
-
The __ can be applied to structures drawn using Fischer projections. The __ can also be determined directly from the Fischer projection, without having to convert it to a perspective drawing.
- Cahn-Ingold-Prelog
- R or S configuration
-
Explain the directions of the Fischer projection.
If te molecule demonstrates R, it is actually S when drawn in the regular structure
-
Fischer projections are most useful for what?
Asymmetric carbons are where?
The vertical lines and horizontal lines do what?
- compounds with two or more asymmetric carbon atoms
- the centers of crosses
- vertical go away
- horizontal go toward viewer
-
The carbon chain is placed where?
The entire projection can be rotated what?
Interchanging any two groups on an asymmetric carbon does what?
- along the vertical, with the IUPAC numbering from top to bottom
- 180 but nott 90 without changing the stereochemistry
- inverts its stereochemistry
-
We've defined __ as isomers whose atoms are bonded together in the same order but differ in how the atoms are directed in space. All other stereoisomers are classified as __, which are stereoisomers that are not mirror images. Most __ are either __ or compounds containing what?
- stereoisomers
- diastereomers x2
- geometric isomers
- compounds containing two or more chirality centers
-
One class of diastereomers are __, which are not mirror images of each others, making them diastereomers.
- cis-trans isomers
- (geometric isomers)
-
Cis trans isomerism is also possible when what?
there is a ring present
-
Apart from geometric isomers, most other compounds that show diastereomerism have what?
two or more chirality centers, usually asymmetric carbon atoms
-
A compound with n asymmetric carbon atoms might have as many as __ isomers. This formula is called the __.
-
What is the 2^n rule?
- n is the number of chirality centers (usually asymmetric carbon atoms)
- the 2^n rule suggests we should look for a maximum of 2^n stereoisomers
-
Compounds that are achiral even though they have asymmetric carbon atoms are called __.
What is the typical structure of them?
- meso compounds
- the two similar halves of the molecule have opposite configurations
-
In speaking of two diastereoisomers, the symmetric one is called the __, and the chiral one is called the __, since one enantiomer is __ and the other is __.
- meso diastereomer
- (±) diastereomer
- (+)
- (-)
-
Meso compound
an achiral compound that has chirality centers (usually asymmetric carbons)
-
The term meso was used to what?
describe an achiral member of a set of diastereomers, some of which are chiral
-
The optically inactive isomer seemed to be where between the what?
- in the middle
- dextrorotatory and levorotatory isomers
|
|