Introduction to Organic Chemistry Section 10.1

Organic Chemistry The chemistry of carbon compounds Not including metal carbonates and oxides Are varied and substantial in numbers Energy sources, food, drugs, and other materials Extensive because of carbon's bonding capability

Carbon Group 4 Has 4 valence electrons Always forms 4 covalent bonds in organic molecules All single bonds: tetrahedral shape Oxygen forms 2 bonds Hydrogen and the halogens form one

Carbon Bonds with Carbon Carbon can not only combine with itself, but with other atoms (especially H and O) to form millions of compounds Basis of life (known) The C-C (348 kJ mol -1 ) and C-H (412 kJ mol -1 ) bonds are very strong and stable

More Carbon Stuff Catenation: chemical linkage into chains of atoms of the same element Strength of the bonds allow the long chains and rings to form Stability of the bonds cause the structures to be unreactive Multiple bonds have increased chemical reactivity, as well as other atoms such as O, N, and the halogens

Functional Groups An atom or group of atoms attached to an organic molecule that contains elements in addition to carbon and hydrogen Examples are O, N, and the halogens Organic compounds are made of a hydrocarbon skeleton to which functional groups are attached.

Homologous Series/Class A series of compounds that only differ in the presence of an additional -CH 2 unit (methylene group) Can be represented by a general formula Have similar chemical properties Have physical properties that vary in a regular manner as the number of carbon atoms present increases

Intermolecular forces The greater the molar mass of a molecule, the stronger the intermolecular forces Some functional groups change the polarity within the molecule, so dipole-dipole forces cause slightly higher melting and boiling points. Some functional groups have hydrogen bonding occur so these melting and boiling points are much higher than non-polar or polar compounds with similar mass

Changes in Physical Properties Strength of London dispersion forces Increasing molar mass Change in molecular polarity Steep initial change because of the proportionally large change in molar mass % change becomes smaller as the chain length increases, so the slope is shallower Applies to other physical properties like density and viscosity

Solubility Most organic compounds are non-polar and usually are insoluble Those with functional groups can hydrogen bond to the water and will be soluble if the hydrocarbon chain is short Increase in chain length = decrease in solubility Carboxylic acids act as weak acids Amines act as weak bases

Formulas Empirical: gives the simplest whole number ratio of each type of atom (C 2 H 4 O) Molecular: gives the actual number of each type of atom (C 4 H 8 O 2 ) Structural: indicates how the atoms are arranged (CH 3 CH 2 CH 2 COOH) or condensed: CH 3 (CH 2 ) 2 COOH Full structural: shows all the atoms and bonds

Other Standard Representations R represents an alkyl group ROH represents an alcohol Benzene ring is Phenol is HO─

Isomers Different compounds that have the same molecular formula Have different physical properties May have different chemical properties Two main types Structural isomers: atoms are joined in a different order, different structural formulas Stereoisomers: order of joining is the same, but the arrangement in space is different

Structural Isomers Three main types: positional, hydrocarbon chain, and functional group Positional isomers have similar chemical properties, as do hydrocarbon chain isomers Positional: same hydrocarbon skeleton, same functional group, but the functional group is joined to a different part of the skeleton

Hydrocarbon Chain Isomer Have different hydrocarbon skeletons that the functional group is attached to

Functional Group Isomers Some functional groups have an isomer with another functional group Example: ethanol and methoxymethane Can be very different as far as physical and chemical properties are concerned