Summary:

Organic chemistry might also be called carbon chemistry, because carbon C is the basis of all organic compounds. The word "organic" means that many organic substances are or were building blocks of living matter, though it is now possible to create most of them artificially.


Molecules of hydrocarbons contain a chain of carbon atoms, connected by Aromatic hydrocarbons have a circular structure (a closed ring of the carbon chain), e.g., benzene C6H6. Derivatives of hydrocarbons are formed by substituting hydrogen atoms by more reactive elements (halogens Cl,Br,I,F) or by functional groups (e.g. methyl -CH3 , ethyl -C2H5, hydroxyl -OH /alcohols/, carboxyl -COOH /acids/, amine -NH 2 groups).
A reaction between two molecules of alcohol gives ethers, characterised by -O- group (R-OH + R-OH-H2O+R-O-R), e.g., the well known anaesthetic diethylether C2H5-O-C2H5 is obtained from ethylalcohol C2H 5-OH in a catalytic reaction. Fermentation of alcohols produces ketones, which are characterised by the group -CO-, e.g., the frequently used solvent acetone CH3-CO-CH3 is produced from propanol (CH3-CH-OH-CH3 - CH3-CO-CH3 + H2). Oxidation of alcohols is also used for preparing carboxylic acids (characterised by the carboxyl group -COOH), e.g., benzoic acid C6H5-COOH, which is used for preserving foods. As you see, alcohols are not only for drinking!

Polymers are formed by chaining monomers in polymerisation reactors (the addition or condensation reactions are performed at very high pressure and temperature, when some multiple bonds of monomers are released and the free sites enable connection of monomers to the long chains). Copolymers, polymers with chains consisting of two different monomers, should be distinguished from alloys and blends, which are only mixtures of several polymers.
Polymers that can be repeatedly heated up to the plastic state are called thermoplasts, while thermosets are polymers which are irreversibly cured at a high temperature and cannot be melted or processed again.
The most common polymers (click here for more extended survey from Endura Plastics) are All these polymers, polyolefines, have the common structural pattern

[-C2H 3 R-]

. Other important polymers are
Elastomers are very flexible polymers characterised by "memory of an initial shape". For example polyamides PA, polyesthers PES, polyuretanes PU and polyolefines are classified as thermoplastic elastomers. Important elastomers include rubbers: The general formula of rubbers is

[-C4H5 R-],

and you see the double bond between the two central carbons - this site is a weak point which can be attacked by oxygen, and this is a main cause of the ageing of rubber and other plastics (double bonds are generally less stable than single C-C bonds).

Polymers in the solid state can have an amorphous or crystalline structure. Amorphous polymers are characterised by gradual softening when the temperature increases, and their melting point is not well defined.

Solid Structure: Amorphous Crystalline
Polymer: polystyrene, polycarbonate, acrylic, polysulfone, ABS, SAN Polyethylene, propylene, polyesthers, nylon, acetals
Chemical resistance: atacked by organic solvents resistant to most solvents
Wear: high friction and wear low friction and wear
Optical properties: transparent opaque, refract light rays


Polymers are usually processed in the molten state, by extrusion, by compression or by injection molding. New technologies suitable for Rapid Prototyping are SLA (stereolithography) and SLS (selected laser sintering), which make use of photopolymer resins.

Verses for fun:

PETITIO PRINCIPII

Sad After Night
at a PETting PArty
Please Let me Cry.
PETitio principii


(SAN, PET, PA, PLC)

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@TEC: 3. 3.2003 Change language to English DEFAULT BACKpeoples U218 FS-CVUT Interesting links mailto: Zitny