Lewis acids/bronsted acidity of LA complexes

Question 1

What is a lewis acid?

Answer 1

Electron deficient

Question 2

What is a lewis base?

Answer 2

Electron rich

Question 3

What are acids?

Answer 3

Co-ordinatively unsaturated

They need to be able to accept electrons

Question 4

What do bases have?

Answer 4

Excess electrons in the form of a lone pair or an anion

Question 5

Where are electrons transferred from and to in acids and bases?

Answer 5

From a filled orbital to a vacant orbital

Question 6

Show the general equation for LB and LA reaction?

Answer 6

M+ (LA) + X- (LB) M-X

electrons transferred from X- to the metal

Question 7

What is the mesomeric effect in determining the strength of lewis acids?

Answer 7

Orbital overlab

Question 8

In the mesomeric effect, the heavier the halogen…

Answer 8

The more acidic

Question 9

How do the ligands relate to the acidity?

Answer 9

Small ligands are able to give a better orbital overlap as they have a shorter B-X bond.
Weaker lewis acids

Question 10

What is the trend in acidity from BF3 - BCl3 - BBr3 - BI3 for the mesomeric effect?

Answer 10

Increasing lewis acidity

Question 11

What is the inductive effect?

Answer 11

The electronegative atoms surrounding the central atom withdraw the electrons, meaning the central atom is more electron deficient and this means that it is a stronger lewis acid

Question 12

What is the trend in acidity from SiF4 - SiCl4 - SiBr4 - SiI4 for the inductive effect?

Answer 12

Decreasing lewis acidity

Question 13

In the electronegative effect, the lighter the halogen…

Answer 13

the more acidic

Question 14

What is an aqua complex?

Answer 14

Metal with H2O ligands

Question 15

In an aqua complex, what happens to the likelihood of releasing a proton by having the metal present?

Answer 15

Increases

Question 16

What does acidity depend on in aqua complexes?

Answer 16

oxidation state and ionic radius

Question 17

What is acidity governed by in aqua complexes?

Answer 17

Electrostatic interactions

Question 18

What is the acidity like of a small ion aqua complex with a high oxidation state?

Answer 18

Strong acid

Stable conjugate base

Question 19

What is the acidity like of a large ion aqua complex with a low oxidation state?

Answer 19

Weaker acid

Less stable conjugate base

Question 20

How are polymers of aqua acid formed?

Answer 20

Condensation reaction - removal of water

This is facilitated by a bronsted base

Question 21

What condition does the polymerisation of aqua acids happen?

Answer 21

Basic conditions

Question 22

What does the loss of H2O in the condensation of aqua acids result in?

Answer 22

Bridging oxygen

Question 23

What would most metal hydroxides be classed as?

Answer 23

Basic

Question 24

What does acidity depend on for hydroxo acids?

Answer 24

Ionic radius and charge

Question 25

What can oxoion be stabilised by?

Answer 25

A strong enough acid

Question 26

How does the acidity of a hydroxo acid compare to an aqua acid?

Answer 26

They are much less acidic

Question 27

What happens to the hydroxo acids?

Answer 27

Complex is deprotonated to form the conjugate base which is then stabilised

Question 28

How does charge of hydroxo acid complexes relate to acidity?

Answer 28

The higher the charge, the more ionic interactions to stabilise the conjugate base

Question 29

What is the oxo group in a metal oxo acids?

Answer 29

M=O double bonds

Question 30

Which block of oxoacids does Pauling’s rule apply to?

Answer 30

P-block

Question 31

What does the oxyanion resonate with?

Answer 31

The oxogroup

Question 32

What are the relative acidities of oxoacids, aqua acids and hydroacids?

Answer 32

Oxoacids>aqua acids>hydroacids

Question 33

How are polyoxo anions formed?

Answer 33

Condensation reaction - removal of water

Question 34

What is acidic polymerisation?

Answer 34

Start with a base and add protons