chem 40a - final

rules for aromaticity

1) cyclic & planar

2) each atom in cycle = sp2 hybridized

3) Huckel’s rule - # of e- = 4n+2 (n=any integer)

naming carbons - 1

methane

naming carbons - 2

ethane

naming carbons - 3

propane

naming carbons - 4

butane

naming carbons - 5

pentane

naming carbons - 6

hexane

naming carbons - 7

heptane

naming carbons - 8

octane

naming carbons - 9

nonane

naming carbons - 10

decane

resonance rules

pi bonds, lone pairs, p orbitals, same overall charge

constitutional isomers (aka structural)

same molecular formula, different connectivity

conformational isomers

same molecular formula & connectivity, vary by orientation

stereoisomers

type of conformational isomers, can be a/chiral

stereoisomers - enantiomer, diastereomer, epimer

enantiomer - all stereocenters = inverted

diastereomer - 2+ but not all stereocenters = inverted

epimer - only 1 stereocenter = inverted

stereogenic/chiral center

sp3 hybridized, 4 different substituents

alkenes nomenclature - cis (Z)/trans (E)

cis (Z) - C=C double bond = same side on parent chain

trans (E) - C=C double = opp side on parent chain

mass spectrometry - key outputs

base peak - highest intensity peak

molecular ion peak - mw of ionized sample, heaviest, Br = signature 2 similar intensity peaks with 2 neutrons apart

Acids definition

Bronsted - H+ donor

Lewis - e- pair acceptor

Base definition

Bronsted - H+ acceptor

Lewis - e- pair donor

pKa of hydronium ion

0, strong acid

pKa of protonated alcohols

0, strong acid

pKa of protonated carbonyls

0, strong acid

pKa of alcohols

15, strong base

pKa of amines

35, strong base

pKa of alkanes

60, strong base

pKa of hydrochloric acid

-7, strong acid

pKa of protonated amines

10

pKa of carboxylic acids

5

pKa of thiols

10

pKa of protonated imines

7

pKa of water

15

pKa values to predict equilibrium - equation & meaning

10^[(pKa_f)-(pKa_i)], if <1 = rxn unfavorable, >1 = rxn favorable

acidity increases if:

low pKa, periodic trends (south-east), resonance (greater stability), induction (greater = more acidic)

basicity periodic trend

increases north-west

physiological pH = ~7, functional groups with pKa < 6 are:

deprotonated

physiological pH = ~7, functional groups with pKa > 8 are:

protonated

nucleophilicity

1) protonation state - deprotonated = more nucleophilic

2) periodic trend - horizontal: R to L, vertical: depends on solvent

3) resonance - more acidic, less basic = less nucleophilic

4) steric effects - greater steric bulk = less nucleophilic

electrophilicity

1) steric effects - increase bulk, decrease reactivity

2) carbocation stability - tertiary = stablest, savors Sn1

leaving groups are good if:

weaker bases, highly acidic

Sn1 favored if:

LG = strong acid/weak base, nucleophile doesn’t matter, stable carbocation intermediate, polar protic solvent, sterically blocked

Sn2 favored if:

strong anionic nucleophile, LG = strong acid/weak base, polar aprotic solvent

identifying biomolecules - carbs

CHO, 1:2:1, ring shape

identifying biomolecules - lipids

CHO, hydrocarbon chain + glycerol group

identifying biomolecules - proteins

CHON, amine group

identifying biomolecules - nucleic acids

CHONP, phosphate group