Chapter 4: Analyzing Organic Reactions Flashcards
What are lewis acids
electron acceptors; vacant orbitals or positively polarized
What are lewis bases
electron donators; lone pair/anions
what are bronsted lowry acids
proton donators
what are bronsted lowry bases
proton acceptors
what are amphoteric molecules
act as both bases/acids
what is Ka
acid dissociation constant; measure of acidity; HA –> H+ + A-
what is pKa
-log(Ka) ; lower pKa = stronger acid
what is the trend of pKa on the periodic table
decreases down the periodic table and decreases with an increase of electronegativity
what are alpha hydrogens
hydrogens connected to the alpha carbon; acidic
what are common basic functional groups
amines and amides
what are common acidic functional groups
alcohols, ketones, carboxylic acids, aldehydes
what are nucleophiles
contain lone pairs or pi bonds; increased electron density; often carry a negative charge
difference between nucleophilicity and basicity
nucleophilicity = kinetic
basicity = thermodynamic
what affects nucleophilicity
charge, electronegativity, steric hinderance, solvent
what are electrophiles
contain a positive charge/positively polarized; more positive = more electrophilic
what are leaving groups
molecular fragments that retain the electrons after heterolysis
what makes a good LG
resonance stabilization/induction; weak bases
what is an Sn1 reaction
1) LG leaves forming carbocation
2) Nucleophile attacks carbocation from either side forming racemic mixture
What makes for a good Sn1 reaction
more substituted carbons because alkyl groups donate electron density to stabilize carbocation
What determines the rate of Sn1
concentration of substrate
what is an Sn2 reaction
Nucleophile attacks at the SAME time LG leaves
what is specific about an Sn2 reaction
Backside attack = inversion of stereochemistry
what makes for a good Sn2 reaction
less substituted carbons for less steric hinderance for the backside attack
what is the rate of Sn2 reaction depended on
concentration of substrate and nucleophile
what is oxidation
increase in oxidation state ; assisted by oxidizing agents
what are oxidizing agents
accept electrons and reduced in the process; high affinity for electrons
primary alcohol –> aldehyde
PCC
primary alcohol –> carboxylic acid
CrO3 ; Na2Cr2O7 ; K2Cr2O7
secondary alcohol –> ketone
any oxidizing agent
what is reduction
decrease in oxidation state ; assisted by reducing agents
what are reducing agents
donate electrons and oxidized in the process
aldehydes, ketones, carboxylic acids –> alcohol
LiAlH4
amides –> amines
LiAlH4
esters –> diols/pair of alcohols
LiAlH4
how do you protect aldehydes and ketones
diols
how do you protect alcohols
conversion to tert-butyl ethers
