Chemistry 30 Organic Chemistry NOTES

I. Organic Chemistry Definition Organic compounds are those obtained from living organisms. Inorganic compounds are those obtained from minerals. Organic compounds are those obtained from living organisms. Inorganic compounds are those obtained from minerals. Organic Chemistry is the study of molecular compounds of carbon (except oxides and carbonates). Of the approximately 10 million compounds discovered, 90% are molecular compounds of carbon. Carbon is unique because it can form 4 bonds (4 bonding electrons), and can form chains, rings, spheres, and can form combinations of single, double, and triple bonds. Organic Chemistry is the study of molecular compounds of carbon (except oxides and carbonates). Of the approximately 10 million compounds discovered, 90% are molecular compounds of carbon. Carbon is unique because it can form 4 bonds (4 bonding electrons), and can form chains, rings, spheres, and can form combinations of single, double, and triple bonds.

I. Organic Chemistry Hydrocarbons Hydrocarbons can be divided into two main categories Hydrocarbons can be divided into two main categories Aliphatics Aliphatics Aromatics Aromatics

II. Aliphatics 1. Alks : C n H 2n+2 1. Alkanes : C n H 2n+2 Carbon – Carbon single bonds Carbon – Carbon single bonds

II. Aliphatics - Alkanes These are compounds composed of carbon and hydrogen whose carbon – carbon bonds are all single bonds (saturated). Hydrocarbons containing carbon – carbon double or triple bonds are said to be unsaturated. Alkanes in which the carbon atoms form long “strings” or chains are called normal, straight chain, or unbranched hydrocarbons.

2. Types of Formulas a) Molecular formula Example: C 2 H 6 b) Expanded molecular formula Example: CH 3 CH 3

c) Structural formula Example: d) Condensed structural formula Example: Example: e) Line Structural formula Example: Example:

3. Structural Isomers Hydrocarbons can have the same number of atoms but are arranged differently; these are called. Hydrocarbons can have the same number of atoms but are arranged differently; these are called structural isomers. Example: C 4 H 10 can be written as normal or branched normal or branched

4. Nomenclature (Naming) of Alkanes a) normal alkanes: each is named according to the stem plus the ending -ane. Stem Prefix# of CarbonsFormulaName meth1CH 4 methane eth2C2H6C2H6 ethane prop3 C 3 H 8 propane but4C 4 H 10 butane pent5C 5 H 12 pentane hex6C 6 H 14 hexane hept7C 7 H 16 heptane oct8C 8 H 18 octane non9C 9 H 20 nonane dec10C 10 H 22 decane

Each of these names can have an “n” in front to indicate normal Each of these names can have an “n” in front to indicate normal Example: n-butane Example: n-butane

b) Branched alkanes: follow these steps i. i. Find the longest continuous chain ii. ii. Number the carbon atoms starting at the end closest to the branch (if more than one branch is present, start at the side that will result in the lowest numbers) iii. iii. When alkane groups appear as branches, they are named by dropping the –ane and adding –yl. For example methane becomes methyl. These are called alkyl groups and branches. iv. iv. Name the branch first, indicating its number, then a hyphen followed by the stem name. v. v. The branches are listed in alphabetical order and the prefixes di-, tri-, etc. are used to indicate multiple, identical branches.

c. Examples: i. Heptane ii. 3 - methylheptane

iii. 2, 4 – dimethylheptane

iv. 3-ethyl-4,7-dimethyldecane

v. n-butane vi. 2,3 – dimethylbutane

vii. Draw all 5 structural isomers of C 6 H 14

5. Drawing Structural Diagrams from Names Start with the number of carbons in the longest continuous chain, then add branches where needed. Start with the number of carbons in the longest continuous chain, then add branches where needed.

6. Cyclic Alkanes: C n H 2n Carbon atoms can form rings. The simplest is cyclopropane. These bonds are unusually weak or strained so it is more reactive than normal propane. The same rules apply for naming but the prefix cyclo- is added. Carbon atoms can form rings. The simplest is cyclopropane. These bonds are unusually weak or strained so it is more reactive than normal propane. The same rules apply for naming but the prefix cyclo- is added.Example: cyclopropane: C 3 H 6

More examples: Cyclobutane: C 4 H 8

1-ethyl-2-propyl 1-ethyl-2-propylcyclobutane

Properties of Alkanes Physical Properties Physical Properties Nonpolar results in London Dispersion Forces Nonpolar results in London Dispersion Forces C1 – C4: gases (cooking, heating) C1 – C4: gases (cooking, heating) C5 – C16: liquids (camping fuel, auto gas) C5 – C16: liquids (camping fuel, auto gas) C16 > wax like solids C16 > wax like solids Fairly unreactive because saturated bonds are strong (good for plastics, lubricants) Fairly unreactive because saturated bonds are strong (good for plastics, lubricants) Refining: physically separating HC mixtures (coal and natural gas) Refining: physically separating HC mixtures (coal and natural gas) Petroleum refining: boil petroleum and separate on basis of boiling point (fractional distillation) Petroleum refining: boil petroleum and separate on basis of boiling point (fractional distillation)

Properties of Alkanes Chemical Properties Chemical Properties Cracking – done to meet extra demand for smaller alkanes (gasoline C5 – C12) Cracking – done to meet extra demand for smaller alkanes (gasoline C5 – C12) Thermal cracking – high heat, no oxygen Thermal cracking – high heat, no oxygen Catalytic cracking – catalyst used, no oxygen Catalytic cracking – catalyst used, no oxygen heat or catalyst C17H36(s) + H2(g) → C9H20(l) + C8H18(l)

Reforming – converts low grade gasoline into higher grade, makes synthetic lubricants and petrochemicals Reforming – converts low grade gasoline into higher grade, makes synthetic lubricants and petrochemicals heat or catalyst C5H12(l) + C5H12(l) → C10H22(s) + H2(g) C5H12(l) + C5H12(l) → C10H22(s) + H2(g)

Combustion – burning of fuels, incomplete combustion forms CO(g) Combustion – burning of fuels, incomplete combustion forms CO(g) C17H36(s) + O2(g) → CO2(g) + H20(g) Substitution – reactions where one atom or group substitutes a H atom Substitution – reactions where one atom or group substitutes a H atom CH4 + Cl2 → CH3Cl + HCl