Introduction to Organic Chemistry Flashcards
Stereochemistry
defined by the spacial arrangement of atoms in molecules
Stereoisomerism
the relationship between isomers which have the same connectivity but different spatial arrangements of atoms in space (configuration/stereochemistry)
Relative stereochemistry/configuration
When the stereochemitry drawn on a molecule distinguishes “this diastereomer”; tells is only how the stereogenic centres within a molecule relate to each other
i.e. 2-methylcyclohexanol has 2 possible relative configurations (cis or trans) based on the relative positions of the two substituents but there are 4 configurational isomers with absolute configuration
Absolute stereochemistry/configuration
when the stereochemistry drawn on a molecule distinguishes this enantiomer of this diastereomer - i.e. R and S enantiomers of a molecule describe their absolute configurations
Enantiomer
non-superimposable object and mirror images of each other : hence always come in pairs
Diastereoisomer
stereoisomers which are NOT related by being enantiomers (e.g. achiral usually)
Meso compound
An achiral member of a set of diastereoisomers which includes at least one chiral member
Achiral
a molecule or object which has a superimposable mirror image
Racemate
A mixture which contains equal parts of two enantiomers such that it is optically inactive
Epimer
One of a pair of diastereomers which has opposite configuration at only one stereocentre out of at least two.
Atropisomerism
Compounds which are chiral because of restricted rotation about a single bond
Conformation
Any spatial arrangement of atoms of molecules that can be achieved by rotation about single bonds
Configuration
The spatial arrangement of atoms which distinguishes stereoisomers
Constitution
Constitution of a molecule is defined by the sequence of bonds (atom connectivity) between atoms without reference to their directions in space
i.e. consitutional isomers have the same molecular formula but different connectivity
A stereogenic centre or stereocentre (chiral centre)
A carbon atom (or other atom) bearing 4 different substituents
What does it mean for a solution to be optically active
Rotates the plane of plane polarised light
Separated enantiomers rotate the plane of plane polarised light in equal but opposite directions
what is syn-addition to a double bond
addition to the same face
what is anti-addition to a double bond
addition to the opposing faces of a double bond (i.e. one on the top face and one on the bottom face)
enantioenriched
consisting of an excess of one enantiomer
enantiopure
consisting of a single enantiomer
racemisation
the conversion of one enantiomer (or an excess of one enantiomer) into a 50:50 mixture of enantiomers
Lewis Base
electron pair donor
Lewis acid
electron pair acceptor
Why are amides less basic than amines
Less electron density on N as the lone pair is delocalised into the carbonyl group making it harder to donate (and less favourable due to the stabilisation provided by conjugation)
