Organic Chemistry Substitution Quiz

How to form an alkyl halide?

radical reaction

What is the first step in a radical reaction?

Initiation

What is the second step in a radical reaction?

Propagation

What is the third step in a radical reaction?

Termination

What is initiation?

The formation of a radical from a halogen gas

What is propagation?

Creation of a radical from a alkyl halide and the end product

What happens to the rate of the reaction when activation energy increases?

Rate decreases

Resonance & Radicals

More resonance = more stable

Exothermic vs endothermic halogenation

Exothermic is not selective or impacted by carbocations, endothermic is

What do radical reactions require on the arrow?

Heat or light (hv)

Anti-Markovnikov Bromination solvents

ROOR

Allylic bromination

Attacks H on allylic carbon instead of double bond

Allylic bromination solvent

NBS

Substitution reactions

Nucleophile replaces leaving group (halogen)

“Good” leaving group

willing to leave, determined by strength of bond

Good nucleophiles

Atomically large, charged (too many e-), localized, polarizable, not resonant

SN2 energy diagram

one step concerted process, leaving group leaves as nucleophile attacks

SN2 Mechanism

inversion/backside attack —> inversion of stereochemistry

SN2 Orbitals

SN2 reactions not possible on sp² hybridized carbon

order of reactivity

1>2>3

SN2 & Steric strain

steric strain increases Ea and slows reaction

SN2 Solvents

polar aprotic

SN2 effect of nucelophile & electrophile

stronger Nu, faster rate; smaller E, faster rate

SN2 Rate law

[alkyl halide][nucleophile]

SN1 Energy Diagram

two step process w/ discrete carbocation intermediate

order of reactivity

3>2>1; more stable carbocation = more reactive

SN1 Stereochemistry

forms racemic mixtures: both enantiomers

SN1 Solvents

polar protic: hydrogen bonding

SN1 Rate determining steps

Slow: R-X —> R+ + X+

Fast: Nu + R —> Nu-R

SN1 Rate law

k[R-X]