Unit 2 - Acids and Bases

Bronsted-Lowry Acid

Donates proton

Bronzted Lowry Base

Accepts proton

Low pKa

Strong acid

The stronger the acid

The weaker the conjugate base

Equilibrium prefers the

weaker side

A more stable CB

Stronger acid

ARIO

Assess neutral to anionic acid reactions

Atom Charge

Atoms more electronegative, or larger in AR can stabilize a negative charge better

Resonance

Spreading negative charge across multiple atoms makes it stabler

Induction

Stabilizing negative charge with electronegative atoms

Quantity Effect

More electrons withdrawing atoms stabilizes charges more

Proximity Effect

Closer electron withdrawing atoms are to charge, the more effective

Quality Effect

More electronegative atoms stabilize better

Orbital Type

Electrons closer to nucleus are more stable (sp to sp³)

Exception to ARIO

Alkene + anionic nitrogen molecules must have pka values to assess

ARIO for Cationic Acids

The more stable cationic acid, the more basic and less acidic

Atoms for Cationic Acids

Less EN atoms with charge will be less acidic/more basic

Resonance for Cationic Acids

Localized lone pairs on CB are basic/less acidic because a localized lone pair is more available to function as a base

Induction for Cationic Acids

Less neighbouring EN atoms makes cations more basic

Orbital for Cationic Acids

Charges further from a nucleus are better stabilized (sp³ to sp²)

Predicting Equilibrium

1. Identify the acids, HA & CA of Base

2. Compare pkas, if pKa of HB > pka HA, product is favoured

Equilbrium Equation

K_eq=10^{pkaHB - pkaHA}

In basic solution, base can’t be stronger than

CB of solvent (OH)

In acidic solution, acid can’t be stronger than

CA of solvent (H3O)

Predicting Level Effect

1. Identify solvent CA or CB

2. If acid is stronger, pka < pka_solvent or base if stronger, CA pka > pka_{CA solvent} it’ll protonate solvent

Solvating Effect

If a compound is hindered from groups, it’ll be weaker because solvent can’t surround negative charge

Counterions

Spectator ions, usually group 1 or nitrates are always there

Lewis Acid

Accepts electron, electrophilic

Lewis Base

Electron donor, nucleophile

Aspirin

Originated from salicylic acid with an addition of acetyl to make it more absorbable

Chromatography

Separation method base on polarity, using a polar stationary phase and a non polar mobile phase

Stationary Phase

Solid to separate compounds

Mobile Phase

Liquid to separate compound

Chromatography Method

Compound is added to solid phase on top, and mobile is poured through, dragging non-polar species through quicker than polar species

Retention Time t_r

Measure of time compound takes to pass through the column

If mobile is too polar

Polar molecules won’t stick to a solid and pass too fast

If solid is too non-polar

Molecules will pass too slowly

Reverse Phase Silicia

Highly non-polar

Thin Layer Chromatography

Analyzes a small amount of compound using an aluminum plate covered with silica gel and a mobile phase at the bottom of a bottle

Thin Layer Chromatography Method

Non-polar molecules will travel with the mobile phase, and polar molecules will move slower

Extraction

Using solvents that naturally separates and dissolve compound where it naturally dissolves depending on polarity

Polar molecules dissolve in

Water

Non-polar molecules will dissolve in

Organic solvents 

Hydrophilic Organic Molecules

4 or less carbon chain with a functional hydrogen bonding group

Extraction Method

Everything is mixed and placed in a separatory funnel, mixed then filtered

If organic solvent is denser than water

It’ll partition on top, usually chlorinated solvents

Carboxylate Salt

COOH + NaOH or NaHCO₃

Phenolate Salt

Phenol + NaOH

Ammonium Salt

Amine + HCl

Crystallization

Soluble compound remains in liquid, and unsoluble crystallizes out as it cools down