Izod L7-9 Flashcards
Describe germanium chemistry
Ge very similar to Si: +4 oxidation states dominate but +2 accessible. Ge-X bonds stronger than expected due to X->Ge hyperconjugation, but overlap of X l.p with Ge-X σ* poorer therefor weaker σ bond and hyperconjugation.
What oxidation state does Sn adopt
Sn both +4 and +2 oxidation states dominate accessible
What oxidation state does Pb adopt
Pb +2 oxidation states dominates
Describe SnX2 compounds
SnX2 compounds are Lewis acids as they are electron deficient but are also also Lewis bases because they have a lone pair. For example SnCl2 polymerises with stereochemically active lone pair.
Define catenation
Catenation is the ability of an element to form bonds with itself, creating chains or rings of atoms of the same element
Describe catenation for Si and Ge
Si and Ge forms long chains
Describe catenation for Sn
For Sn mostly cycles
Describe E=E for group 14
C=C sigma and pi orverlap very good. For Ge-Pb valence orbitals are large/diffuse therefore very poor pi overlap so E=E is quite rate.
Describe electron configuration for group 15
Ground state electron configuration ns2np3
Describe the oxidation states for group 15 elements
+3 oxidation state common for all elements
+5 for N,P,As,Sb
Describe ammonia
Ammonia produces by harber-Bosch process
N2 + 3H2 -> 2NH3
Industrially used in fertiliser and explosives. NH3 has high b.p due to extensive H bonding (N-H - - - N) used as a solvent
Describe hydrazine
N2H4 produced by oxidation of ammonia. Good reducing agent readily oxidised by O2
N2H4 + O2 -> N2 + 2H2O
Used as rocket propellant
Describe nitrogen monoxide
NO colourless gas, odd electron radical species. Unpaired electron in delocalised pi* orbital therefore not stable
Describe nitrogen dioxide
Radical (singly occupied molecular orbital localised on N atom) therefore reactive.
What is the equilibrium of NO2 with and what does it depend on
2NO2 in equilibrium with N2O4 and position of equilibrium controlled by temperature and pressure.
Describe nitric acid and the reaction if is synthesised by
Nitric acid is a very strong acid and synthesised by catalysed oxidation of NH3
NH3 + 2O2 -> HNO3 + H2O
Nitric acid is also a strong oxidising agent
Describe how HNO3 oxidised Cu
4HNO3 + Cu —> Cu(NO3)2 + 2NO2 + 2H2O
Describe nitrogen halides
NF3 - stable gas very unreactive
NCl3 - volatile liquid explosive
NBr3/NI3 - too reactive/ e plosive for isolation
Describe what structure phosphorus prefers
P prefers pyramidal structure eg P4
Why is N2 more stable than P2
For N, N triple bond N much stronger than 3xN-N for P, P triple bond P much weaker than 3xP-P. P-P favoured
Describe phosphorus hydrides
PH3 - toxic gas
P2H4 - not common
What are phosphorus main oxides
Two main oxides
- P4O6
- P4O10
What are the phosphorus oxoacids
Phosphoric acid
Phosphonic acid
Phosphinic acid
Describe the phosphorus trihalides
All trihalides known, very useful for synthesis of phosphines, insecticides, plasticisers, flame retardants.
Oxidise/hydrolyse readily
Write the oxidation and hydrolysis of PCl3
PCl3 + 1/2O2 -> Cl3P=O
PCl3 + 3H2O -> H3PO4 + 3HCl
Describe the bonding in PF5
Forms 5 bonding but only has 4 valence orbitals (3s and 3x3p). P atom hypervalent. Bonding explained using multi-centre bonding scheme.
Describe the hydrides of As, Sb, Bi
Very toxic, increasingly unstable down group. Poor E-H sigma overlap.
Describe the halides of As, Sb, Bi
All trihalides know/stable buy penrahalides confirmed to EF5 not know EBr5 and EI5
Describe the oxides of As, Sb, Bi
All E2O6 known
Only As2O5 known due to inert lone pair effect
Describe the ground state electron configuration of group 16
Ground state electron configuration ns2np4
What are the common oxidation states for group 16
2,4,6
What are the hydrides for oxygen
H2O, H2O2
Describe H2O2 and its reactions acting as an oxidising agent, reducing agent and how it can disproportionate
Can act as an oxidising agent
H2O2 + 2H+ + 2e- -> 2H2O
And a reducing agent
H2O2 -> O2 + 2H+ +2e-
Can disproportionate
2H2O2 —> 2H2O + O2
Describe the oxygen halides
Only fluorides known
OF2 - colourless poisonous gas
O2F2 - yellow liquid below -100 degrees, structure similar to H2O2
Describe the sulphur hydrides
Only H2S important. H2S very toxic
List the sulfur oxides and describe them
Most stable oxides are SO2 and SO3
SO2 - toxic gas at room temperature by product of burning fossil fuels
SO3 - toxic gas at room temperature
List the sulfur fluorides
S2F2
SF2
S2F4
SF4
S2F10
SF6
List the know sulfur chlorides
SCl2, S2Cl2
Describe S-N compounds
S4N4
Kinetically stable but thermodynamically unstable
S4N4 —> 1/2 S8 + N2
