A molecule which is not superimposable on it mirror image (asymmetric)
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What is the most common feature in chiral molecules?
Presence of an sp3 hybridised C atom carrying four different groups
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What is an achiral C atom?
Possess a plane of symmetry, bisecting angle between bonds with C
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What is an enantiomer?
A chiral molecule and its mirror image. They have identical physical properties e.g. mp, bp, solubilities. Enantiomers are optical isomers
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How can the enantiomers interconvert to form different configurations?
Break bonds
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Which properties are different in enantiomers?
Activities with plane polarised light and different biological effects due to different shapes
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How do you draw a chiral/stereogenic centre?
Two bonds in the plane of paper (thin), one bond behind paper (dash) and one bond in front of paper (solid)
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What is the name given to an enantiomer which rotates the plane of polarised light to right/clockwise?
Dextrorotatory (+)
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What is the name given to an enantiomer which rotates the plane of polarised light to left/anti-clockwise?
Laevorotatory (-)
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Which factors does rotation depend on? (4)
Path length, concentration, wavelength of polarised light and temperature - expressed in terms of physical constant, specific rotation
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How do you calculate the specific rotation?
Observed rotation in degrees / path length x concentration
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Do enantiomers rotate light in opposite directions?
Yes
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Does the rotation from enantiomers relate to the shape of the molecule?
No
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Which two systems are used to describe the precise shape of enantiomers?
D and L, R and S
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What was the Fischer convention mainly used for?
Sugar molecules (assumptions about glyceraldehyde) and amino acids (NH2 may take place of OH)
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What are the key aspects of the Fischer convention?
Draw longest C chain vertically with highly oxidised group at top (vertical bonds below paper/dash), horizontal bonds point up (solid), mirror images can be formed
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Which name is given to the image with OH on the right?
D (+)
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Which name is given to the image with OH on the left?
L (-)
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What is the Cahn-Ingold-Prelog system?
Precise description of configuration of enantiomers. No reference to an arbitrary standard, no need for special drawing convention. Groups assigned priority. Designation depends on sequence of priority
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What is the name given when the priority descends clockwise/right?
R
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What is the name given when the priority descends anticlockwise/left?
S
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How do you name a molecule with more than one stereocentre?
Use the same rules for one stereocentre on each chiral carbon
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How do you work out how many isomers there are for a molecule
2^n where n is the number of stereocentres
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What are diastereoisomers/diastereomers?
Enantiomeric pair (different physical properties e.g. melting points)
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Which prefix is given to compounds with similar groups on the same side?
Erythro
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Which prefix is given to compounds with similar groups on opposite sides?
Threo-
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Other cards in this set
Card 2
Front
What is the most common feature in chiral molecules?
Back
Presence of an sp3 hybridised C atom carrying four different groups
Card 3
Front
What is an achiral C atom?
Back
Card 4
Front
What is an enantiomer?
Back
Card 5
Front
How can the enantiomers interconvert to form different configurations?
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