Organic Chemistry Exam 3

I am a weak base

What are examples of STRONG nucleophiles

High electron density, great at donating electrons

What are examples of GOOD nucleophiles

Good electron density , good at donating protons

What are examples of WEAK nucleophiles

Low electron density, bad at donating protons

What are examples of STRONG bases

What are examples of WEAK bases

What are examples of GREAT leaving groups

What are examples of GOOD leaving groups

What are examples of POOR leaving groups

What are examples of polar protic solvents

What are examples of polar aprotic solvents

What are examples of non-polar solvents

Sn2 reaction properties

Nucleophile: Must be strong

Leaving Group: Good/great

Solvent: Polar aprotic

Alkyl Halides: 1>2>3 (almost no reaction)

Reaction mechanism: 1 step (concerted)

Sterochemistry: Proceeds through inversion only

Rearrangements aren’t possible

E2 Reaction Properties

Nucleophile: Strong base needed

Leaving Group: Good/great

Solvent: Polar aprotic

Alkyl Halides: 3>2>1(only with strong bulky bases)

Reaction mechanism: 1 step with H and RX being antiperiplanar (concerted) 

Sterochemistry: Based on mechanisms

SN1 Properties

Nucleophile: Usually weak

Leaving Group: Great

Solvent: Polar protic

Alkyl Halides: 3>2>1 (almost no reaction)

Reaction mechanism: 2 steps (1. Removal of the leaving group, 2. Addition of nucleophile)

Stereochemistry: Proceeds through inversion and retention

Rearrangements are possible with Carbocation intermediates

Can form Hydrogen Bonds

E1 Reaction Properties

Nucleophile: Weak or strong (usually weak)

Leaving Group: Great

Solvent: Polar protic

Alkyl Halides: 3>2>1

Reaction mechanism: Stepwise Carbocation intermediate 

Sterochemistry: Products must be trans due to cis steric strain 

RX and H dont need to be antiperiplanar

Oxidation

Decrease in C-H bonds, increase in C-O bonds (or equivalent)

Reduction

Increase in C-H bonds, decrease in C-O bonds (or equivalent C-Cl, C-Br, etc).

Acidity of Alkynes

Sp3 is weakest acid

Sp2 is middling acid

Sp is strongest acid

alkyl halide vs vinyl halide vs aryl halide

Alkyl halide: one or more halogen atoms bonded to Sp3 hybridized carbon

Vinyl Halide: halogen attached to a double bond

Aryl Halide: Halogen attached to an aromatic ring

How do Alkyl Halides change going down on periodic table

-they increase in size

-their carbon-halogen bonds increase in size

-their bond strength decreases

Steps of Radical Mechanisms

1. Initiation: breaking a stable molecule into two radicals (initiated by light hv)

2. Propagation: radical species bonds to a stable making one stable molecule and another radical

3. Termination: two radicals combine to form more stable molecules with no other products

Radical Chlorination (reactivity) and Radical Stability Patterns

Both reactivity and stability increase as you increase the amount of substituents on the carbon that aren’t Hydrogen

Alkyl Halides from Alcohols

Tertiary alcohol reacts with HCl or HBr

Primary and Secondary Alcohols react with SOCl2 and PBr3

What is a Grignard reagent

When an alkyl halide reacts with Mg and a solvent, usually followed by some kind of weak base to substitute these alkyl halides

Gilman Reagents

-Makes a C-C bond into an sp2 or sp3 hybridized carbon atom 

-Removes RX from molecule

-Usually used for Sn2 reactions

-(R)2CuLi

Suzuki-Miyarua Reaction

-used to couple two sp2 hybridized carbons

-Pd(PPh3)4 [pd catalysts]& KOH [strong base]

Difference of reaction graph for Sn1 and Sn2 when using polar protic vs polar aprotic for both

Sn1: Lowers reaction energy

Sn2: Speeds up reaction

Sn2 reaction graph effects

-protic v aprotic

-good v poor nucleophile

-hindered vs unhindered substrate

-good leaving group v poor leaving group

-aprotic makes the reaction reach the product faster

-good nucleophile makes the reaction reach the product faster

-unhindered substrate decreases energy for first step

-good leaving group decreases energy for first step