CHM2210 Exam 2

chiral

carbon w/ 4 different substituents

enantiomers

pair of molecules who are mirror images of each other

diastereomers

pair of molecules who are NOT mirror images of each other

R/S

assigned by priority, has to do with chirality

R

approaching from the top, chirality

S

approaching from the bottom, chirality

fischer projections

chiral C in center, substituents coming from center; wedges are horizontal, dashes are vertical, if H is horizontal flip S/R

meso

when a chiral C has a plane of symmetry, it is achiral and _____

racemic mixture

50% (R) and 50% (S)

pro-chirality

one step away from being chiral, re and si can be assigned in place of R/S

specific rotation

observed rotation divided by (grams/solvent) times length in dm (1 dm = 10cm)

enantiomer composition

observed rotation over rotation of pure enantiomer

enantiomeric excess

specific rotation (low) over specific rotation (high)

addition

type of rxn where reactants are added together

elimination

type of rxn where something is removed from the rctnt, can be E1 or E2

substitution

type of rxn where some of the starting rctnt is swapped out, can be SN1 or SN2

rearrangement

type of rxn where the rctnt is changed to a more stable form

homolytic

single electron, free-radical mechanism

heterolytic

electron pairs, ionic (polar) mech

high temperature

favors entropy (delta s)

low temperature

favors enthalpy (delta h)

large K/rate

favors product

small K/rate

favors reactant

Ea

activation energy, larger = slower, RDS is slower

sterics

orientation of the molecule as they collide

nucleophilic

e- rich, attacks electrophiles

electrophilic

e- poor

nucleophilic attack

proton transfer

carbocation rearrangement

delta g neg high t

endothermic, ΔS up, T up

delta g neg

exothermic, ΔS up, T up

delta g pos

endothermic, ΔS down, T up

delta g pos high t

exothermic, ΔS down, T down

SN2

substrate; methyl > 1 > 2 »» 3 (3 doesnt happen)

SN2

nucleophile; very important

SN2

LG; important

SN2/E2

solvent; polar, aprotic

SN1

substrate; 3 > 2 »»1

SN1

nucleophile; irrelevant

SN1

LG; critical

SN1/E1

solvent; polar, protic

nucleophile

the better ________ usually has a negative sign, larger better if in same column and goes hand in hand with basicity

leaving group

the better the _______, the faster the reaction; conjugate base of strong acids make a good ________________

polar aprotic

this kind of solvent cannot donate protons and is usually h-bonded

polar protic

this kind of solvent can donate protons (has free valence e-) and is usually h-bonded

allylic

C double bonded to C; both SN1 and SN2

vinylic

halide double bonded to C; no SN1 or SN2

zaitsev’s rule

the more substituted an alkene, the more stable; tetrasub most stable

hoffman product

when a bulky base is used, this product is preferred to zaitsev’s

E1

2-step elimination method

E1

substrates; 3 > 2 » 1

E1

base; weak/moderate base

E1

no antiperiplanar required, high temp

E2

1-step elimination method

E2

any substrate is good

E2

base; strong base

E2

LG and H+ (proton) has to be anti peri-planar (180 degrees) to each other, low temp

methyl substrate

this substrate only does SN2

SN2

strong nucleophile, 1

E2

weak nucleophile, strong base

E2

strong nucleophile, strong base 2 and 3

SN2

strong nucleophile, weak base

SN1/E1

weak nucleophile, weak base

SN2

if negative charge on less electronegative atom, it is a _______ rxn

E2

if large in size, weak nucleophile; can be strong base good for a _________ rxn

strong nuc, strong base

OH-, K-O-, R2N-, MeO-, EtO-

strong nuc, weak base

K-NH2 (amines), R-S-, CN-, N3-, I-, H2S, R-SH, halides

weak nuc, strong base

Kot-Bu, LDA, DBN, DBU (bulky bases)

weak nuc, weak base

H2O, K-OH (alcohols), carboxylic acids, MeOH, EtOH

bulky base

strong base, weak nucleophile; hoffman product preffered

concerted

means single step

degree of unsaturation

equal to amount of double bonds and rings

degree of unsaturation

[(2*number of C)+2-H-X+N]/2

cis

H are on same side of alkene

trans

H are on opposite side of alkene

E

high priority groups on different sides

Z

high priority groups on same side

markonikov’s rule

C-X bond forms on more substituted carbon, or C w/ least H

anti-mark

C-X bond forms on less substituted carbon, or C with most H

hydrobromination

alkene + H-X leads to a markonikov product, alkene + HBr/ROOR leads to an anti-mark product

halogenation

X2 added, w/ H2O ads an -OH

hydration

acid; H3O+ or H2SO4 adds OH, mark product; to avoid rearrangement, HgOAC/H2O, same product; react w/ BH3 THF to get anti-mark

hydrogenation

H2/Pt/C addds two H groups; cis/syn, react with MCPDA for two line/wedge attach to O (removes the alkene)

dihydroxylation

OsO4/NaHSO4 yields H and OH cis, can react with KMnO4/NaOH when basic pH, cis-1,2-diol forms

cleavage

O3/ZnH+ yields an aldehyde or ketone, when KMnO4 is acidic/neutral yields carboxylic acid

carbene

makes cyclic alkenes by KOH

simmons-smith

H2I2/ZnCu or Et2O yields cyclic alkene

SN1

SN2

E2

E1

hydroboration

BH3 THF yields H and OH both cis