Organic Chem Flashcards
Stability of carbocations
more substitutied are more stable, less substituted are less stable
stability of carbanions
less substituted are more stable, more stubstituted are less stable
constitutional isomers
same molecular formula, different configuration
conformational isomers
same molecule but differ in their rotation around a sigma bond
anti-gauche-syn conformation
anti is most stable, gauche is in middle, syn is least stable
stereoisomers
molecules that have the same atoms and connectivity but different spatial arrangements
assigning priority in steroisomers
- highest atomic number gets highest priority
- isomers with highest weight get higher priority
- In case of a tie, follow to next closest atom
- multiple bond is counted as two single bonds
right hand rule of assigning priority
face lowest priority group into the paper, clockwise rotation means it is R, counterclockwise is S
Fischer projection
spine faces into page, arms face out
enantiomomers
non-superimposable mirror images
diastereomers
non-superimposable, non-mirror images
how to tell the difference between diasteromers and enantiomers
enantiomers have both chiral centers switched, diastereomers only have 1 switched
racemic
only enantiomers are racemic
epimers
subset of diastereomers that differ at one chiral center, OH on the right is a D sugar, OH on th lefts is an L sugar
anomers
epimers that form as a result of ring closure, alpha is down, beta is up on the anomeric carbon
meso compounds
when one side of a molecule is a mirror image of the other side, are not optically active
determining Z and E conformation
highest priority on same side = Z
highest priority on opposite side = E
extraction of organic amines
use a weak acid, protonates the amine, giving a positive charge, making it soluble in aqueous layer
extraction of carboxylic acids
use a weak base to deprotonate the acid, giving it a negative charge, making is soluble in aqueous layer
extraction of phenols
use dilute NaOH to deprotonate, making it soluble in aqueous layer
TLC separation is by…
polarity, stationary phase is polar, so less polar molecules travel further
Rf
the distance a sample travelled in TLC divided by the solvent front, it is always positive and less than 1, higher = travelled further, less polar
reverse phase HPLC
usually has a non-polar stationary phase so more polar compound elute first
size exclusion chromatography
counter-intuitive, larger molecules travel faster through the gel, and smaller molecules get caught
gas chromatography
mobile gas phase and liquid stationary phase, occurings from different volatilities, the more volatile components spend less time in the liquid phase and elute first
branching effect on BP
more branches = lower BP, easier to separate molecules
IR C=0
1735-1680, strong
IR C=C
1680-1620
IR C triple bond
2260-2100
IR C triple bond N
2260-2220
IR C-H
3300-2700
IR N-H
3150-2500
IR O-H
3650-3200, broad
How to read NMR
- number of unique hydrogens correspond to number of signals
2.
formula for degree of unsaturation
(2*Carbons+2-H)/2
splitting
determine the number of neighboring hydrogens and then add 1
