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Advanced Higher - Unit 3

Advanced Higher - Unit 3. Permeating aspects of organic chemistry. What is Organic Chemistry. The chemistry of compounds of carbon. Except Simple oxides of carbon e.g. CO and CO 2 Carbonates e.g. K 2 CO 3 , Na 2 CO 3 , etc. Other simple ionic salts e.g. (NH 4 ) 2 CO 3 , KCN, etc.

cameron-butler
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Advanced Higher - Unit 3

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  1. Advanced Higher - Unit 3 Permeating aspects of organic chemistry

  2. What is Organic Chemistry • The chemistry of compounds of carbon. • Except • Simple oxides of carbon e.g. CO and CO2 • Carbonates e.g. K2CO3, Na2CO3, etc. • Other simple ionic salts e.g. (NH4)2CO3, KCN, etc.

  3. Why is carbon so special? • Five billion compounds have been identified. • More than 95% of these as compounds of carbon yet carbon only makes up 0.2% of the Earth’s crust.

  4. The ability of carbon to form such a huge variety of compounds is due to important properties of the carbon atom itself: - carbon atoms can form four strong covalent bonds with a wide variety of other elements. - carbon atoms can form strong bonds with other carbon atoms giving rise to molecules containing chains of carbon atoms, which can be straight or branched.

  5. - carbon atoms can form molecules containing carbon atoms (and sometimes other atoms) arranged in rings. - carbon atoms can form multiple bonds with other carbon atoms and with oxygen and nitrogen atoms.

  6. What’s So Important About Organic Chemistry? • The largest branch of Chemistry • Organic Chemistry is the Chemistry of • Food production • Medicine • Clothing manufacture (synthetic fibres and dyes) • Plastics • Fuels • Detergents • Life itself!!

  7. Reaction types of organic compounds • Addition Reaction • Two or more molecules combine to produce a larger molecule and nothing else. e.g. CH2= CH2 + H2 CH3- CH3 • Condensation • Two or more molecules combine toform a larger molecule, with the elimination of a smaller molecule (usually water). e.g. CH3OH + HOOCCH3 CH3OOCCH3 + H2O • Hydrolysis • A large molecule is broken into smaller molecules by reaction with water. e.g. CH3CH2Cl + H2O  CH3CH2OH + HCl

  8. Oxidation • Increasing the proportion of oxygen:hydrogen in a compound. e.g. CH3CH2OH  CH3COOH • Reduction • Increasing the proportion of hydrogen:oxygen in a compound. e.g. CH3COOH  CH3CH2OH • Substitution • Replacement of an atom or group of atoms in a molecule. e.g. CH3-CH3 + Br2 CH3- CH2Br + HBr • Elimination • The elements of a simple molecule, like water, are removed from an organic molecule and not replaced. e.g.CH3CH2OH  CH2= CH2 + H2O

  9. Bond Breaking • All chemical reactions involve bond breaking and bond making. • Bond breaking is endothermic and involves the redistribution of electrons between the two atoms. • For a covalent bond there are 2 possible outcomes when it breaks (sometimes called bond fission). • How a bond breaks will determine the mechanism by which a reaction proceeds. • REMEMBER a covalent bond is a shared pair of electrons.

  10. Some Important Symbols Single Headed Arrow - Shows the movement of one electron during bond forming or breaking. Double Headed Arrow - Shows the movement of two electrons during bond forming or breaking. Single Dot - Shows an unpaired electron in a free radical. Two Dots - Usually represents a lone pair of unbonded electrons (occasionally it can be used to represent a covalent bond, i.e. H:Cl)

  11. X—Y  X• + • Y Bond Breaking - Homolytic Fission • The 2 electrons in the bond separate equally - • Homolytic fission results in two electrically neutral species (species - atoms or groups of atoms). • Species with unpaired electrons are know as FREE RADICALS. • Free radicals are highly reactive. • Homolytic fission is more likely when the bond is non-polar.

  12. X—Y  X+ + :Y- H3C+—Br - H3C+ + Br- Bond Breaking - Heterolytic Fission • The 2 electrons in the bond go to one atom - • Heterolytic fission results in the formation of two ions. • Heterolytic fission is more likely when the bond is polar. e.g.

  13. H HC+ H CH3C+ CH3 H H CH3C+ H Carbocation and Carbanions • Carbocation - A positive ion where the charge is on the carbon. e.g. Generally R+ • Carbanion - A negative ion where the charge is on the carbon. e.g. (CH3)3C- , etc. Generally R- • Both carbocations and carbanions are highly reactive and therefore usually short-lived.

  14. N- H+ H+ H+ Nucleophiles and Electrophiles • Nucleophile - ‘nucleus seeker’ i.e. a species that is electron rich and therefore attracted to a positive charge. e.g. Anions - OH-, carbanions, etc. Atoms with lone pairs of electrons e.g. the nitrogen atom in ammonia

  15. O- H+ H+ • Electrophile- ‘electron seeker’ i.e. a species that is electron deficient and therefore attracted to a negative charge. e.g. Cations - H+, Na+, carbocations. A partially positive atom in a polar covalent compound, e.g. the hydrogen atoms in water.

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