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Organic Chemistry

Alkanes & Cycloalkanes combustion

Alkane substitution (Cl2, Br2) (CH4 + Cl2 => CH3Cl + HCl)

Free Radical substitution: homolytic fission

Initiation Br2 => Br. + Br.

Propagation

Termination CH3. , Br. recombine

Unsaturated hydrocarbons

Hydrogenation - catalyst (Pt)

React with Cl2, Br2 - no catalyst

Water {acid catalyst} => alcohol

Isomers => Markovnikov's Rule

HCl / HBr already acidic

Part 2

Alcohol => hydroxyl

OH group polar, hydrogen bonding

Can be formed by the hydration of alkenes
Alkenes may be re-formed by eliminations reactions

Primary secondary tertiary

Aldehyde - terminal (-al)

Ketone - middle (-one)

=> Carbonyl C=O

Ether => ether (-oxy)

R-O-R'

Carboxylic acids => carboxyl (-oic acid)

R-COOH

Ester (-oate)

R-COO-R

Amine => amino

R-N

Amide => amide

R-CO-N-R

Nitrile => nitrile

R-CN

SP hybridized carbon, Short strong polar triple bond

Slideshow 2

A) Alkanes - see above

B) Oxidation of alcohol (+ O, heat)

Primary and Secondary alcohols can react with KMnO4, [Cr2O7]2-

Reduction of Aldehydes, Ketones

LiAlH4, NaBH4

Only time H- is nucleophile - attracted to positive C of C=O bond

Dry ether

Esterification - condensation

Carboxylic Acid + Alcohol, heated, acid catalyst

Slideshow 3

Nucleophilic substitution

Usually OH-

Sn2 - bimolecular - one step, backside attack - primary leaving group

Better in aprotic solvents (ex propanone / acetone)

Sn1 - unimolecular - 2 steps - tertiary halogenoalkanes

1) {Slow} Leaving group gets electron pair; Carbocation forms (much more stable as tertiary)

2) Nucleophile attacks carbocation, leaving group attracted to H

Steric hindrance

Carbocations stabilized by A) # of carbons attached; B) # of pi bonds; C) # of adjacent lone pairs (N, O, Cl)

Protic solvents preferred (water, alcohols, carboxylic acids)

Leaving group

Rate: Sn1 (carbocation) faster than Sn2 (steric hindrance)

Free Radical Substitution

(see Slideshow 1)

Slideshow 4

Electrophilic Addition

Unsaturated; pi electrons are nucleophile

CH3CH=CH2 + HCl => CH3-(CClH)-CH3

CH2=CH2 + Br2 => Br-CH2-CH2-Br

Hydrogen Halide reaction

May form stereoisomers if carbon is chiral.

Halogen reaction: induced polarization

Dihalogenoalkanes, steric hindrance

Bimolecular 1st step slow

Iodine should be faster than Fluorine

Benzene Electrophilic Substitution

Slideshow 6

Structural, Stereo

Conformation, Configuration

cis-trans / EZ, Optical

E Z

1) Higher atomic number is priority

2) Longer carbon chain is priority

Enantiomers

Racemic mixture