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Organic Chemistry. The unique chemistry of carbon. Learning objectives. Describe two reasons for abundance of carbon compounds Distinguish between inorganic and organic carbon and other compounds Distinguish between isomers and non-isomers

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Organic chemistry

Organic Chemistry

The unique chemistry of carbon


Learning objectives
Learning objectives

  • Describe two reasons for abundance of carbon compounds

  • Distinguish between inorganic and organic carbon and other compounds

  • Distinguish between isomers and non-isomers

  • Describe differences between optical and geometric isomerism

  • Distinguish between aromatic and non-aromatic

  • Identify common functional groups


One element one branch of chemistry
One element – one branch of chemistry

  • Organic compounds based on carbon: 13 million and rising (fast)

    • 100,000 new compounds synthesized annually

  • All 91 other elements combined: only 300,000 compounds


Factoids about carbon
Factoids about carbon

  • Fairly abundant in earth’s crust – but not enough to explain domination


Highly significant to life
Highly significant to life

  • Key element in the human organism – and all others


God s goof the absence of stable mass 5
“God’s goof”: The absence of stable mass 5

  • C and O are abundant because the atom with mass 5 is unstable

  • Otherwise atom building after the Big Bang would have resulted in much heavier elements

  • The thoughts of a cosmological atheist Fred Hoyle:

    “Some supercalculating intellect must have designed the properties of the carbon atom, otherwise the chance of my finding such an atom through the blind forces of nature would be utterly minuscule….The numbers one calculates from the facts seem to me so overwhelming as to put this conclusion almost beyond question”


Organic and inorganic carbon
Organic and inorganic carbon

  • Inorganic carbon: ionic compounds where carbon is incorporated as carbonate – CO32-

  • Organic carbon: compounds of carbon with itself, hydrogen and other elements – by far the most important


Organic carbon forms a thin canopy
Organic carbon forms a thin canopy

  • Unique (?) conditions on earth that support life

Earth’s surface - organic

Earth’s crust - inorganic


Vitalism and organic chemistry
Vitalism and organic chemistry

  • Inorganic compounds were salts of the earth

    • Stable and easily synthesized

  • Organic compounds were of living organisms

    • Fragile and not easily synthesized

  • Belief in Vitalism posited that only living organisms possessed a vital force necessary to create organic compounds

  • In 1828 urea was synthesized and vitalism was on the way out


Seven ages of man many ages of a carbon atom
Seven ages of man - many ages of a carbon atom

  • Combustion: C + O2 CO2

  • Neutralization by seawater: CO2 + Ca(OH)2  CaCO3 + H2O

  • Reaction with acid rain: CaCO3 + H2SO4  CO2

  • Photosynthesis: CO2  Organic compounds (OC)

  • Vegetation decomposes: OC  fossil fuels (FF)

  • Vegetation consumed by animal: OC  new compounds (proteins, DNA etc.)

  • Respiration: sugars  CO2 + energy

  • Industrialization: FF  C, CO2 + energy

  • Manufacturing: FF  Plastics, polymers, drugs etc.

  • Waste disposal Fossil fuels, CO2


Two reasons why carbon is unique
Two reasons why carbon is unique

  • Carbon can form four bonds – four valence electrons

  • Carbon forms very strong bonds with itself – chains, rings etc.



Hydrocarbons are the simplest organic compounds
Hydrocarbons are the simplest organic compounds

  • Contain only C and H

  • Simplest is CH4 (natural gas)

  • Intermediate C8H18 (petroleum)

  • Synthetic polymers contain thousands of atoms


Alkanes
Alkanes

  • All bonds are single

  • Saturated

  • No new bonds can be added

  • General formula CnH2n+1



Representing molecules
Representing molecules

  • Molecular formula

    • Shows atoms in the molecule

  • Structural formula

    • Shows how they are all connected

  • Condensed structural formula

    • Simplified representation of connections


Naming organic compounds
Naming organic compounds

  • Meth - ane

Number of carbon atoms

Type of compound



Saturation bonding multiple bonds and unsaturation
Saturation bonding:Multiple bonds and unsaturation

  • Saturated: no more bonds can be added

  • Unsaturated: more bonds can be formed

    • More reactive compounds


Alk ene s contain double bonds
Alkenes contain double bonds


Going bananas ethylene and fruit ripening
Going bananas: Ethylene and fruit ripening



Isomerism
Isomerism

  • Same number and type of atoms

  • Different arrangements

  • Hydrocarbons can have straight and branched chains


Isomers simplified
Isomers simplified

  • Alkane isomers

    • General formula CnH2n+1

  • Three isomers of pentane

    • C5H12

  • Five isomers of hexane

    • C6H14


Number of isomers mushrooms as chain length increases
Number of isomers mushrooms as chain length increases

  • CH4 – 1 possibility

  • C2H6 – 1

  • C3H8 – 1

  • C4H10 – 2

  • C5H12 – 3

  • C8H18 – 18

  • C10H22 – 75

  • C20H42 – 366,319


Optical isomerism is a special variation
Optical isomerism is a special variation

  • Molecules exhibit handedness – mirror images which are not super-imposable

  • Must have tetrahedral carbon with four different groups attached

  • This carbon is chiral


Isomers and reaction yield
Isomers and reaction yield

  • Each chiral carbon produces two isomers

  • If there are n chiral carbon atoms there are 2n isomers


Optical isomers are important in nature
Optical isomers are important in nature

  • Amino acids are building blocks of proteins

  • Amino acids are chiral

  • Proteins contain hundreds – thousands of amino acids

  • Getting the correct isomer is a big deal


Geometric isomers isomerism and a healthy diet
Geometric isomers: Isomerism and a healthy diet

  • What’s with all this trans fats anyway?

  • Ask a Chicago Alderman

  • Different geometry - same attachments

  • Cis isomers:

    • Don’t pack together

    • Cis isomers have low viscosity - good

  • Trans isomers:

    • Pack together tightly

    • Trans isomers are solids - bad


Aromatic the stuff of dreams
Aromatic: the stuff of dreams

  • Benzene ring contains 6 C atoms

  • Bonding is resonant – more stable than expected

  • All aromatic compounds contain at least one benzene ring

  • Benzene, C6H6, is one of the most important industrial chemicals


Toxicity of benzene
Toxicity of benzene

  • Benzene is regarded as a highly carcinogenic substance

  • Use and disposal of benzene are regulated

  • Compounds containing benzene rings are not necessarily toxic


Functional groups
Functional groups

  • Chemistry of organic compounds is determined by functional groups

  • Functional group is an atom or group of atoms that are different from C

  • Heteroatoms confer very different properties on the substance


Heteroatoms affect physical and chemical properties
Heteroatoms affect physical and chemical properties

  • C2H6 (ethane) is a gas at RT

  • C2H6 is insoluble in water

  • C2H6O (ethanol) is a liquid at RT

  • C2H6O is soluble in water

    • Differences in cohesive forces: O-H bonds are polar, C-H bonds are not



Chlorocarbons and the environment
Chlorocarbons and the environment

  • Important uses – important problems

    • Solvents CH2Cl2

    • Insecticides DDT

    • Refrigerants CFCs


Alcohols hic
Alcohols: hic

  • Functional group –OH

  • Polar molecules dissolve in H2O

  • Ethanol: good for your health/bad for your health?


Smoke gets in my eyes olefactory pleasures of aldehydes
Smoke gets in my eyes: olefactory pleasures of aldehydes

  • C=O is carbonyl group

  • Aldehyde contains RCHO

  • Formaldehyde is a preservative and a product of burning wood

  • Acrolein is a product of barbequing

  • Common smells and flavours


Ketones
Ketones

  • Ketone is R1R2CO

  • Acetone is a common solvent

  • Smell found in cinnamon

  • Raspberries


Carboxylic acids
Carboxylic acids

  • Commonly found in citrus fruits and any sour foods

  • Formic acid present in ant and bee stings


Esters sweet aromas and flavours
Esters: sweet aromas and flavours

  • Ester group is R1COOR2

  • Sweet aroma in pineapples, jasmine

  • Synthetic versions are very common


Ethers
Ethers

  • Ethers contain R1-O-R2

  • No -OH bonds

  • Not soluble in water

  • Anesthetics


Amines the stench of death
Amines: the stench of death

  • Amines contain NR1R2R3

  • Rotting fish

  • Decaying flesh

  • Illicit drugs


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