the element with the most compounds known most of the compounds are considered to be organic what...

The element with the most compounds known

Most of the compounds are considered to be organic

What defines an organic compound? Compound is made by an organism and

found in nature as part of an organism or stemming from an organism

Inorganic carbon compounds

The electronic structure of Carbon: 1s22s22p2

The C4+ ion does not exist A unique feature of Carbon is its self

binding properties. It can form single, double and triple

bonds, and forms stable chains. The C_C bond is thermodynamically very

stable and strong.

Chemistry and Physical Properties of Diamond, Graphite, Fullerenes, adn Carbides

Diamond – Graphite: differ in their properties because of the differences in the arrengement and bonding

Density of Diamond is higher, graphite is more stable

Graphite can be transformed into Diamond at 3000K adn pressures above 125kbar. AS catalysts Cr, Fe or Pt.

Chemial reactivity of Diamond is lower then graphite or amorphous carbon.

Graphite: Amorphous carbon: many forms are

microcrystalline forms of graphite. Physical properties of these materials are

mainly determined by their surface area. The large surface forms: Absorb large amounts of gases and

solutes. Carbon, doted with Pd, Pt are uysed as industrial catalysts.

Fullerenes: C60 Buckminster fullerene or Buckyball

fullerene. Birch reduction: Unsaturation of C60 by Li in NH3/t-BuOH The other chemistry of fullerenes is with

organic molecules (we are not going through this).

C60 can react towards transition metals an η2 connection to Pt or Ir is made by the π electrons of a C=C group

Partial Halogenation can be achieved with reaction with Cl2 or Br2

C60 + Br2 C60Br2 or C60 Br4

At 150 deg C Br2 can be recovered C60 + Cl2 C60Cln (n=24 at average) At t>400deg C dechlorinate. Alkali metals results in black materials

(K+)3C603-.

Films of C60 doped with K,Rb or Cs metal vapor are superconducting. RbnC60 is 30 K.

Carbides Solid compounds with elements other

than H are generally called carbides. Classification of Carbides: Ionic Carbides

Alkali and alkaline earth metals and Al.

Interstitial Carbides Reactions with transition metals. The

metals occupy tetrahedral holes in the close packed arrays of metal atoms.

Materials are very hard, conducting, and have high melting points (3000-4800 deg C).

WC is hard, used for machining steel. Cr,Mn,Fe,Co,Ni are between ionic and

interstitial. Hydrolysed by watere and dilute acids.

Covalent Carbides: Si, B form SiC B4C hard, chemically inert.

SiC has diamond like structure in which C and Si are tetrahedrally surrounded by four of the other kind of atoms.

Carbon Monoxides

A mixture of CO and Hydrogen is used as synthesis gas in the synthesis of Methanol.

Carbon monoxide is formally the anhydride of formic acid (HCO2H).

Most important property is its ligand towards transition metals.

Only Fe and Ni react directly with CO (toxic).

Carbon dioxide Found in the atmosphere, volcanic gases

and in some spring water. Large scale released from fermentation

processes, limstone calcination, combustion of C and Carbon compounds.

Involved inn Photosynthesis. Solid CO2 (-78.5 deg C) Carbonic acid

Carbonic acid: Hydration occurs pH<8 direct hydration

pH>10 direct attack with OH-

Cyanides and Related Compounds Most important inorganic cemistry is the

C-N bonds. The most important species are Cyanide,

Cyanate, Thiocyanate ions. Cyanogen (CN)2 Flammable gas

Cu catalysed production of Cyanogen

Dry (CN)2 is made from

Hydrogen cyanide HCN is a covalent molecule Can dissociate in aqueous solution Poisonous colourless gas High dielectric constant Due to hydrogen bonding Liquid HCN can polymerize Aqueous solutions polymerize inducer is UV

light. HCN, water, Ammonia pentamerizes to

adenine.

Production of HCN

Cyanides

Transition metal cyanides are water insoluble

Ag and Au cyanides are of importance. Others are used analytically.

Compounds with C-S bonds CS2 is a very reactive molecule, is a liquid

and is toxic.

Carbon disulfide is one of the samll molecules that readilyundergo insertion reactions.

Si, Ge, Sn,Pb Si most abundant element in Nature

afdter O Ge, Sn, Pb are rare elements Sn,Pb have been known since long time,

because they can be just melted out of their minerals

Ge was discovered after its existance has been predicted.

It is purified from coal and zinc ore concentrates

Multiple bonding It has been long thought that Si and the

other elements of group IV do not form multiple bonds

But:

At 500 degC

Although compounds are similar in stoichiometry they do not share structural or chemical similarity.

CO2 is a gas, SiO2 is a network forming molecule with each Si atom bonded to four O.

Silane alcohols when dehydrated give polymers, not like the alkenes from carbon.

Compounds having oxidation state IV form tetrahedral compounds

But valence shell expansion using outer d-orbitals can occur (dsp3 or d2sp3)

5 and 6 coordinate compounds are common.

5 coordination:

Si is obtained by reductionof SiO2 with carbon or CaC2 in an electric furnace.

Ge is prepared by reduction with C or H2. Si and Ge are mainly used in

semiconductirs. The element is first converted to a tetra

chloride, reduced back to the metal by hydrogen at high temperatures.

After casting into rods it is refined by zone melting.

Sn and Pb are made by the reduction of the oxide or sulfide with carbon.

Si is rather ureactive. It reacts with halifdes and alkali giving silicates.

It is only attack by HF acid. Ge is a bit more reactive. Dissolves in

conc H2SO4 and HNO3. Sn,Pb dissolve in several acids, react with

halogens. Slowly react with cold alkali, fast with hot alkali.

Colorless gases. Only SiH4 is of importance. It is used in

the reaction for precursors of silicones. Chlorides: MCl4 gives colorless liquids Exception Pb-- yellow.

The tetrachlorides are hydrolysed by water

To hydrous oxides SiCl4 and GeCL4 are used in the

synthesis of pure Si and Ge and in organic chemistry.

SiO2 occurs as Quartz and cristobalite. Si is always tetrahedrally bound to 4 oxygens. Quartz and criustobalite can be

interconverted by heat. Slow cooling of molten SiO2 will result in

glass. Basic character of the dioxides increases from

Si to Pb. No true hydroxiudes exist.

Anionic complexes

The other F anions are readily hydrolysed by bases.

Cationic complexes Their main application is in organic

chemistry and will not be discussed here.

Si Divalent Si species are thermally unstable But at 1100 degC:

In the frozen state it is stable, when thawing it gives fluorosilanes up to Si16F34

Ge: GeF2 is a crystalline solid and stable. It is obtained by reacting Ge with HF at

200 degC. GeCl2 gives salts similar to the Sn ions. Sn: The most important compounds are: SnF2 and SnCl2

Only Pb has a well defined low valent cationic chemistry.

Most Pb salts are only sparingly soluble in water, PbSO4 and PbCrO4 are insoluble.