Organic Chemistry ACS Review (Mechanisms)

Percent Yield

=100(product mass/theoretical mass)

Diels Alder

forms cyclic hexane from a diene and a dienophile.

Friedel-Crafts

Add acyl or akyl group

Grinard

add alkyl or aryl group

Wolf-Kirschner, Clemmenson

Reduce ketone to alkane

Wittig

Convert aldehyde/ketone to alkene

Transition State

Maximum on the reaction-coordinate curve: least stable intermediate.

Activation Energy (Ea)

Energy of the TS relative to the reactant

Change in enthalpy is <0

for an exothermic reaction.

Change in enthalpy is >0

for an endothermic reaction

Hammond-Leffler postulate

The TS is more like the reactant or product that is closer in energy

An endothermic TS is like

the product

An exothermic TS is like

the reactant

Exergonic

large and negative expelling of energy

A reaction with exergonic DG

has a product likely controlled by thermodynamics

Large Keq corresponds to

large amount of product relative to the reactant

If a reaction has a large Ea

TS controls the reaction instead of product-reactant thermodynamics

When a solvent stabilizes an intermediate

Ea decreases and rate of reaction increases

Charged complexes are stabilized

by polar solvents

Lewis acid

electron pair acceptor

Bronsted lowry acid

proton donor

Lewis base

electron pair donor

bronsted lowry base

proton acceptor

A weak H-A bond

the acid is more likely to donate its proton.

High electronegativity of A (in HA)

increases the strength of the H-A bond, making it harder for the acid to donate its proton.

inductive effect of substituent on A (in HA)

decreases the strength of the H-A bond, making it easier for the acid to donate its proton. (electron withdrawl)

Inductive effect

the electron-withdrawing effect of substituents that stabilizes the conjugate base, enhancing acid strength.

More “s” character in a hybrid orbital

weakens the H-A bond, making the acid stronger.

A resonance stabilized conjugate base A-

Increases acid strength in corresponding HA by delocalizing the negative charge through resonance, thus stabilizing the conjugate base.

A base is

a nucleophile

Nucleophile

a chemical species that donates an electron pair to form a chemical bond in reaction.

Electronic effects shifting electron density

increases base strength

Alkane =

Hydrocarbon with only single bonds

Alkanes have weak

intermolecular forces

Alkanes are non

cyclic (formula C_nH_2n+2)

Alkanes geometry is

tetrahedral around each carbon

Cycloalkane formula

C_nH_2n

Bicyclic

two fused/bridged carbon rings

Cyclopropane distance of an e- from the nucleus

n = 3

cyclobutane distance of e- from nucleus

n = 4

cyclopentane distance e- from nucleus

n = 5

cyclohexane distance of e- from nucleus

n = 6

Cyclopropane structure is

highly strained

cyclobutane structure is

flexible

cyclopentane structure has

slight puckering to minimize angle strain.

cyclohexane stable conformer structure is

chair

cyclohexane less stable structure is

boat

cyclohexane structure perpendicular to plane of the ring is

axial position

cyclohexane structure in plane with the ring is

equitorial position

Cis

two substituents in the upright position

trans

one substituent up and one substituent down

hydrogenation of alkynes to form alkanes

Possible catalysts for hydrogenation of alkynes and alkenes

H2, Pd, Pt, Ni

Free radical reaction of alkene

Reduce haloalkane

possible catalysts in the reduction of haloalkanes to alkanes

Metal hydrides, and metals alongside H giving species (like Mg+H2O), Plutonium, Nickel

Friedel-Crafts alkylation

Friedel Crafts alkylation catalyst

Aluminum Chloride (AlCl3)

Combustion of alkanes

Halogenation to haloalkane

Properties of Alkene

Non-polar, flammable

Nomenclature of Alkenes

Use # to denote the C=C position, add -ene to prefix

Isolated alkene nomenclature

C-C=C-C-C=C-C

Cumulative alkene nomenclature

-C=C=C-

Polyunsaturated fatty acid alkene nomenclature

2 or more C=C

Allene alkene nomenclature

Adjacent C=C=C

Vinyl group alkene nomenclature

H_2C=CH-

Methylene group alkene nomenclature

H_2C=

Allyl group alkene nomenclature

H_2C=CH-CH_2-

Vinyl Halide alkene nomenclature

Halide replaces -H on >C=C<

Conjugated alkene nomenclature

Alternate C-C and C=C (resonance)

Alkadiene

An alkene containing two double bonds, typically in a chain arrangement.

Alkatriene

An alkene containing three double bonds, typically in a chain arrangement.

Annulene

Conjugated monocyclic hydrocarbons with alternating double bonds.

Aromatic cyclic ions

are ions that contain a cyclic structure with conjugated pi electrons, typically displaying resonance stability.

Isomers of alkenes

have no free rotation of C=C

In a non-cyclic alkene

the cis isomer is more stable than the trans isomer due to steric hindrance

In a cyclic alkene

the cis isomer is more stable than the trans isomer due to angle strain and steric interactions.

Hofmann Rule

Form the least substituted alkene

Markovnikof Addition

H adds to the C with the most -H’s and the OH or other group adds to the C with the fewest -H’s.

Zaitsev Elimination

Form the more substituted alkene

Dehydration of alcohols

Dehydrohalogenation of haloalkane

Dehalogenation vicinal dihalide

Hydrogenate alkyne

Alkene combustion

Markovnikov 2 and 3 degree hydration of alkene, 1 degree ethene rearrange

Hydroborate oxidation (anti-markovnikov)

Oxymercuration-demercuration of alkenes to alcohols

Hydrohalogenation of alkenes

Halogenate vicinal dihaloalkane from alkenes

Anti addition of halohydrins from alkenes

Hydroxylation of alkenes to form 1,2-diol

Oxidation of alkenes to carboxylic acid

Ozonolysis of alkenes to form ketone

Hydrogenation of alkenes to alkane

Free radical polymerization of alkenes

Allylic halogenation of alkenes

Diels alder of alkenes

Properties of benzene/arene

Insoluble in water, miscible with non-polar organic solvents