Study Guides (390,000)
CA (150,000)
McGill (6,000)
Chemistry (200)

CHEM 212 Study Guide - Midterm Guide: Valence Electron, Lone Pair, Lewis Acids And Bases

Course Code
CHEM 212
Hanadi Sleiman
Study Guide

This preview shows page 1. to view the full 4 pages of the document.
CH 3
Acids and bases (Bronsted)
Arrhenius def H+ or OH- released in water
Bronsted acid/base def Lose/accept proton
Ka vs Keq Keq = [H3O+][A-] / ([HA][H2O])
Ka = [H3O+][A-]/[HA] = Keq * [H2O]
pKa -logKa
Strong acid
Conj base of strong acid
Use single arrow in reaction formula, =>
Ka > 100
pKa < -2
Weak base
Weak acid
Conj base of weak acid
Use double arrow, <>
Ka between 1 and 10-10
pKa between 0 and 10
Strong base
Conj base of non-acid
Use single arrow, towards water and non-acid <=
Ka < 10-14
pKa > 14
Trends in acidity
Group # (columns
are groups)
Acidity increases with group # of X in HX: strong to weak acid, H-F > H-O > H-N
Electronegativity effect – across the row, more EN => takes electrons from H bond
Period # (rows are
Acidity increases with period #: strong to weak acid, H-I > H-Br > H-Cl > H-F
Bond strength effect – strength decreases as size increases (coulomb’s law)
Also, large anions are more stable bc charge distribution
Hybridization sp more acidic than sp2 more acidic than sp3 esp. in alks: alk(y>e>a)ne acidity
More s character => the electron which the central atom provides are closer to the
central atom => easier to steal. (Note: opposite to period # vs acidity!)
Inductive Organic compounds: electronegative atoms take electrons, making central carbon
atoms more partially positive (positive = acidic); making the compound excluding the
leaving proton more electronegative (acidic); making the anion more stable as the high
EN atom takes neg. charge (acidic).
Higher EN group: more acidic
EN group shorter in distance from leaving proton: more acidic
H3C-CH2-F. Left carbon is less acidic than right carbon.
Resonance Resonant anions are more stable, resonant acids are more acidic
Lewis acid/base
Lewis acid Electron deficient, empty valence orbital
(Do all acids really have an empty valence orbital? Hydronium? Ammonium?
Test this sometime.)
Lewis base Electron rich, lone pair of valence electrons
Lewis acid/base
LUMO: Lowest energy unoccupied molecular orbital (acid)
HOMO: Highest energy occupied molecular orbital (base)
Reaction types
Number of reaction types 4
Reaction Description Context
Substitution One group replaces another Happens to saturated compounds
(sp3), aromatics
Addition Two molecules become one
Reagent adds to substrate
Happens to unsaturated compounds
Elimination One molecules become two
Small molecule eliminated
For preparation of unsaturated
Rearrangement Reorganization of parts of 1 molecule Happens to reactive intermediates
Bond breaking
Number of ways to break bonds 2
Heterolytic bond cleavage (heterolysis) A-B; bond double arrow to B; A+ + :B- (B with lone pair)
Creates ions
Homolytic bond cleavage
A-B; bond single arrow to A and another single arrow to B; A.
and .B radicals
find more resources at
find more resources at
You're Reading a Preview

Unlock to view full version