Lewis acid-base theory
Very different from Brønsted-Lowrey acid-base.
Lewis acid-base theory Very different from Brønsted-Lowrey acid-base. Not dependent on protons or pH.
Lewis acid-base theory An acid is a lone-pair acceptor. Definitions:
Lewis acid-base theory An acid is a lone-pair acceptor. H + no electrons – by accepting 2 electrons it attains noble gas configuration. Definitions:
Lewis acid-base theory An acid is a lone-pair acceptor. H + no electrons – by accepting 2 electrons it attains noble gas configuration. BF 3 electron deficient compound - B needs 2 electrons for noble gas configuration.
B Group III 3 valence electrons
F Group VII 7 valence electrons
B Group III 3 valence electrons F Group VII 7 valence electrons
6 electrons for boron rather than 8 Lewis Acid
Lewis acid-base theory Lewis base: lone-pair donor Definitions:
Lewis acid-base theory Lewis base: lone-pair donor NH 3 N has lone pair Definitions:
Group V Group I
Lewis Base
Lewis acid-base theory Lewis base: lone-pair donor NH 3 - N has lone pair H 2 O - O has 2 lone pairs
Lewis acid-base theory H 3 N : + BF 3 H 3 N : BF 3
Lewis acid-base theory H 3 N : + BF 3 H 3 N : BF 3 Lewis base
Lewis acid-base theory H 3 N : + BF 3 H 3 N : BF 3 Lewis base Lewis acid
Lewis acid-base theory H 3 N : + BF 3 H 3 N : BF 3 Lewis base Lewis acid Both electrons in this bond come from nitrogen.
Lewis acid-base theory H 3 N : + BF 3 H 3 N : BF 3 Lewis base Lewis acid Coordinate covalent bond
(CH 3 ) 3 N BCl 3 (CH 3 ) 3 N : + BCl 3 (CH 3 ) 3 N : BCl 3
(CH 3 ) 3 N BCl 3 (CH 3 ) 3 N : + BCl 3 (CH 3 ) 3 N : BCl 3 This compound may be referred to as an adduct.
CH 3 COOH (aq) + NH 3(aq) NH 4 + (aq) + CH 3 COO - (aq)
CH 3 COOH (aq) + NH 3(aq) NH 4 + (aq) + CH 3 COO - (aq) NH 3 Lewis base
CH 3 COOH (aq) + NH 3(aq) NH 4 + (aq) + CH 3 COO - (aq) NH 3 Lewis base CH 3 COOH is not a Lewis acid.
H + + NH 3(aq) NH 4 + (aq) + CH 3 COO - (aq) NH 3 Lewis base CH 3 COOH is not a Lewis acid. CH 3 COOH(aq) + H 2 O H 3 O + + CH 3 COO -
H + + NH 3(aq) NH 4 + (aq) + CH 3 COO - (aq) NH 3 Lewis base CH 3 COOH is not a Lewis acid. CH 3 COOH(aq) + H 2 O H 3 O + + CH 3 COO - H 3 O + H + + H 2 O
CH 3 COOH (aq) + NH 3(aq) NH 4 + (aq) + CH 3 COO - (aq) NH 3 Lewis base CH 3 COOH is not a Lewis acid. H + is the Lewis acid.
Al(OC 2 H 5 ) 3
Tri-ethoxy aluminum
Al(OC 2 H 5 ) 3 Al is Group III - electron deficient like BF 3.
Al(OC 2 H 5 ) 3 Al is Group III - electron deficient like boron.
Al(OC 2 H 5 ) 3 Al is Group III - electron deficient like boron. This molecule is a Lewis acid.
Al(OC 2 H 5 ) 3 Al is Group III - electron deficient like boron. This molecule is a Lewis acid. O has lone pairs, it is a Lewis base
Al(OC 2 H 5 ) 3 Al is Group III - electron deficient like boron. This molecule is a Lewis acid. O has lone pairs, it is a Lewis base The molecule is both a Lewis acid and base.
x3 Al...
Al(OC 2 H 5 ) 3
Covalent bonds
Al(OC 2 H 5 ) 3 Electron deficient
Al(OC 2 H 5 ) 3 Empirical formula
[Al(OC 2 H 5 ) 3 ] 2 Al(OC 2 H 5 ) 3 Empirical formula Molecular formula
[Al(OC 2 H 5 ) 3 ] 2 dimer
[Al(OC 2 H 5 ) 3 ] 2 dimer Covalent bonds
[Al(OC 2 H 5 ) 3 ] 2 dimer Covalent bonds Coordinate covalent bonds
[Al(OC 2 H 5 ) 3 ] 2 dimer
AlCl 3
Empirical formula
AlCl 3 Empirical formula [AlCl 3 ] 2 Molecular formula
[AlCl 3 ] 2
s block
p block
s block p block Main Group Elements
Oxides of s and p block elements are acid and base anhydrides, with definite trends in respect to the elements’ location in the periodic table.
Oxides of non-metals tend to be acid anhydrides Oxides of metals tend to be base anhydrides
Structure and bonding in s and p block oxides From: N. C. Norman Chapter 5
Norman: Chapter 6 should be read for acid and base information.
Structure and bonding in s and p block oxides From: N. C. Norman Group numbers are changed in Norman.
Groups
Structure and bonding in s and p block oxides Increasing electronegativity
Binary ionic compounds form from elements having very different electronegativities.
Binary ionic compounds form from elements having very different electronegativities.
Oxygen is high on the electronegativity scale, Rb and Ba have the lowest electronegativities of the metals on the Norman chart.
K 2 O : ionic material
K 2 O(s) + H 2 O(l) 2 K + (aq) + O 2- (aq)
K 2 O : ionic material K 2 O(s) + H 2 O(l) 2 K + (aq) + O 2- (aq) O 2- (aq) + H 2 O(l) 2 OH - (aq)
K 2 O : ionic material K 2 O(s) + H 2 O(l) 2 K + (aq) + 2 OH - (aq) Strong base
K 2 O : ionic material K 2 O(s) + H 2 O(l) 2 K + (aq) + 2 OH - (aq) Strong base Base anhydride
Small differences in electronegativities lead to covalent bonds.
Small differences in electronegativities lead to covalent bonds.
SO 3 : covalent molecule
SO 3 (g) + H 2 O(l) H 2 SO 4 (aq) Strong acid
SO 3 : covalent molecule SO 3 (g) + H 2 O(l) H 2 SO 4 (aq) Strong acid Acid anhydride
Some of the polymeric oxides will be amphoteric.
Some of the polymeric oxides will be amphoteric. They will act as acids or bases depending on how acidic or basic the environment is.
Some of the polymeric oxides will be amphoteric. Al 2 O 3 (aq) + 6 H + (aq) 2 Al 3+ (aq) + 3 H 2 O(l)
Some of the polymeric oxides will be amphoteric. Al 2 O 3 (aq) + 6 H + (aq) 2 Al 3+ (aq) + 3 H 2 O(l) Al 2 O 3 reduces H + = basic
Some of the polymeric oxides will be amphoteric. Al 2 O 3 (aq) + 6 H + (aq) 2 Al 3+ (aq) + 3 H 2 O(l) Al 2 O 3 reduces H + = basic Al 2 O 3 (aq) + 2 OH - (aq) + 3 H 2 O(l) 2 [Al(OH) 4 ] - (aq)
Some of the polymeric oxides will be amphoteric. Al 2 O 3 (aq) + 2 OH - (aq) + 3 H 2 O(l) 2 [Al(OH) 4 ] - (aq) Al 2 O 3 reduces OH - : acidic
Structures of polymeric oxides
quartz SiO 4 Empirical formula
quartz SiO 4 Empirical formula
quartz SiO 4 Empirical formula
quartz Tetrahedra share all corners Each share = 1/2 O/Si
quartz Tetrahedra share all corners Each share = 1/2 O/Si
quartz Tetrahedra share all corners Each share = 1/2 O/Si
Binary compounds with halogens
chlorides
NaCl : ionic salt
chlorides NaCl : ionic salt CCl 4 : dense liquid
chlorides NaCl : ionic salt CCl 4 : dense liquid BCl 3 : gas covalent
chlorides AlCl 3 : dimer
chlorides AlCl 3 : dimer GaCl 3 : dimer
chlorides AlCl 3 : dimer GaCl 3 : dimer
chlorides BeCl 2 : infinite chain