Orgo Ch 5 Pt. 1
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What does stereochemistry refer to?
it refers to the 3D properties and reactions of molecules. It has its own language and terms that need to be learned in order to fully communicate and understand the concepts
compounds with the same connectivity, different arrangement in space
stereoisomers that are non-superimposible mirror images; only properties that differ are direction (+ or -) of optical rotation
stereoisomers that are not mirror images; different compounds with different physical properties
sp3 carbon with four different groups attached
the ability to rotate the plane of plane-polarized light
a compound that is optically active (achiral compound will not rotate light)
- device that measures the optical rotation of the chiral compound
- degree at which the light binds
- pol: helps determine whether its optically active
- must bend your lens
handedness: right-hand glove doesn't fit left hand
When is an object chiral?
when its mirror image is different from the original object
Mirror images that can be superimposed upon one another are __
Any molecule that is chiral must have what?
_ is also called an asymmetric carbon atom
Why is it called this?
WHat wll its mirror image be?
- chiral carbon atom
- it is a carbon atom bonded to four different roups that is chiral
- its mirror imae will be a different compound (enantiomer)
An asymmetric carbon atom is the most common example of a __.
__ belong to an even broader group called __. A __ is any atom atom at which the interchange of two groups gives a stereoisomer
- chirality center
- stereocenter (or stereogenic atom)
Asymmetric carbons and the double-bonded carbon atoms in __ are the most common types of __.
- cis trans isomers
Asymmetric carbon atoms are examples of __, which are examples of __.
chirality centers, which are examples of stereocenters
When the images can be superimposed, the compound is __,
A molecule that has a plane of symmetry is __
Achiral compounds can be determined if they have what?
an internal plane of symmetry
If it does not have a plane of symmetry, then what?
the images are nonsuperimposable and the molecule will have two enantiomers
With enantiomers, only one is __. A way to distinguish between them is __ and __.
Enantiomers have what
different spatial arrangements of the four groups attached to the asymmetric carbon
The two possible spatial arrangements are called __.
Each asymmetric carbon atom is assigned __ based on its 3D configuration.
- a letter R or S
__ is the most widely accepted system for naming the configuarions of chirality centers.
What are the rules for R and S config?
- 1) Assign a relative "priority" to each group bonded to the asymmetric carbon
- - atoms wtih higher atomic numbers have higher priorities
- 2) Working in 3D, rotate the molecuels so that the lowest priority groups is in back; rotate from highest to lowest
In case of ties, what do we do?
How to deal with double and triple bonds?
- use the next atoms along the chain of each group as tiebreakers
- treat = and triple bonds as if each were a bond to a separate atom
Properties of enantiomers
- same BP, MP, and density
- same refractive index
- - rotate the plane of polarized light in the same magnitude, but in opposite directions
How do enantiomers react with other chiral molecules?
- different interaction
- -active site of enzymes is selective for a specific enantiomer
- -taste buds and scent receptors are also chiral. Enantiomers have many different smells
Plane-polarized light is what?
composed of waves that vibrate in only one plane
Enantiomers and optical activity
rotate the plane of polarized light in opposite directions, but the same number of degrees
Observed rotation depends on the __ and the __, as well as teh __, __, and __.
- length of the cell
- strength of optical activity
- wavelength of light
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