chemistry 30 organic chemistry notes. i. organic chemistry definition organic compounds are those...
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Chemistry 30Chemistry 30
Organic Chemistry Organic Chemistry NOTESNOTES
I. Organic Chemistry I. Organic Chemistry
DefinitionDefinition Organic compounds are those obtained from Organic compounds are those obtained from living living
organisms. Inorganic compounds are those obtained organisms. Inorganic compounds are those obtained from minerals. from minerals.
Organic Chemistry is the study of molecular Organic Chemistry is the study of molecular compounds of compounds of carboncarbon (except oxides and carbonates). (except oxides and carbonates). Of the approximately 10 million compounds Of the approximately 10 million compounds discovered, 90% are molecular compounds of carbon. discovered, 90% are molecular compounds of carbon. Carbon is unique because it can form 4 bonds (4 Carbon is unique because it can form 4 bonds (4 bonding electrons), and can form chains, rings, bonding electrons), and can form chains, rings, spheres, and can form combinations of single, double, spheres, and can form combinations of single, double, and triple bonds.and triple bonds.
I. Organic ChemistryI. Organic Chemistry
HydrocarbonsHydrocarbons Hydrocarbons can be divided into two Hydrocarbons can be divided into two
main categoriesmain categories AliphaticsAliphatics AromaticsAromatics
II. Aliphatics II. Aliphatics
1.1. AlkAlkaness: C: CnnHH2n+22n+2
Carbon – Carbon single bondsCarbon – Carbon single bonds
II. Aliphatics - AlkanesII. Aliphatics - Alkanes
These are compounds composed of carbon and These are compounds composed of carbon and hydrogen whose carbon – carbon bonds are all hydrogen whose carbon – carbon bonds are all single bonds (single bonds (saturatedsaturated). Hydrocarbons ). Hydrocarbons containing carbon – carbon double or triple containing carbon – carbon double or triple bonds are said to be bonds are said to be unsaturatedunsaturated. .
Alkanes in which the carbon atoms form long Alkanes in which the carbon atoms form long “strings” or chains are called normal, straight “strings” or chains are called normal, straight chain, or unbranched hydrocarbons. chain, or unbranched hydrocarbons.
2. Types of Formulas2. Types of Formulas
a) a) Molecular formulaMolecular formula
Example: CExample: C22HH66
b) b) Expanded molecular formulaExpanded molecular formula
Example: CHExample: CH33CHCH33
c) Structural formulac) Structural formulaExample: Example:
d) Condensed structural formulad) Condensed structural formula Example:Example:
e) Line Structural formula e) Line Structural formula Example: Example:
CH3 CH3
3. Structural Isomers 3. Structural Isomers
Hydrocarbons can have the same number of atoms Hydrocarbons can have the same number of atoms but are arranged differently; these are called but are arranged differently; these are called structural isomers. .
Example: CExample: C44HH1010 can be written as can be written as
normal or branched normal or branched
C C C C C
H
H
H
H
H
H
H
H
H
H
H
HC C C C
H
H
H
H
H
H H
H
C HH
H
H
4. Nomenclature (Naming) of Alkanes 4. Nomenclature (Naming) of Alkanes
a) normal alkanes: each is named according to the stem plus the ending -ane.
Stem Prefix # of Carbons Formula Name
meth 1 CH4 methane
eth 2 C2H6 ethaneprop 3 C3H8 propanebut 4 C4H10 butanepent 5 C5H12 pentanehex 6 C6H14 hexanehept 7 C7H16 heptaneoct 8 C8H18 octanenon 9 C9H20 nonanedec 10 C10H22 decane
Each of these names can have an “n” in Each of these names can have an “n” in front to indicate normalfront to indicate normal
Example: n-butaneExample: n-butane
b) Branched alkanes: follow these steps
i. Find the longest continuous chainii. 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. 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. Name the branch first, indicating its number, then a hyphen followed by the stem name.
v. The branches are listed in alphabetical order and the prefixes di-, tri-, etc. are used to indicate multiple, identical branches.
c. Examples: c. Examples:
i.i. Heptane Heptane
ii.ii. 3 - methylheptane3 - methylheptane
C C C C C C C
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
C C C C C C C
H
H
H
H
H
H H
H
H
H
H
H
H
H
H
C HH
H
iii. 2, 4 – dimethylheptaneiii. 2, 4 – dimethylheptane
C C C C C C C
H
H
H
H H
H
H
H
H
H
H
H
H
H
C
C
HH
H
H
HH
iv. 3-ethyl-4,7-dimethyldecaneiv. 3-ethyl-4,7-dimethyldecane
CH3 CH2 CH CH CH2 CH2 CH CH2 CH2 CH3
CH2 CH3
CH3 CH3
v. n-butanev. n-butane
vi. 2,3 – dimethylbutane vi. 2,3 – dimethylbutane
CH3CH2
CH2CH3
CH3CH
CHCH3
CH3
CH3
vii. Draw all 5 structural isomers of Cvii. Draw all 5 structural isomers of C66HH1414
CH3 CH2 CH2 CH2 CH2 CH3
CH3 CH2 CH2 CH2 CH2 CH3
CH3 CH CH2 CH2 CH3
CH3
vii. Draw all 5 structural isomers of Cvii. Draw all 5 structural isomers of C66HH1414
CH3 CH2 CH CH2 CH3
CH3
CH3 CH CH CH3
CH3
CH3
vii. Draw all 5 structural isomers of Cvii. Draw all 5 structural isomers of C66HH1414
CH3 C CH2 CH3
CH3
CH3
5. Drawing Structural Diagrams from Names
Start with the number of carbons in the Start with the number of carbons in the longest continuous chainlongest continuous chain, then add , then add branches where needed.branches where needed.
6. Cyclic Alkanes: CnH2n
Carbon atoms can form rings. The simplest is Carbon atoms can form rings. The simplest is cyclopropanecyclopropane. These bonds are unusually weak . These bonds are unusually weak or strained so it is more reactive than normal or strained so it is more reactive than normal propane. The same rules apply for naming but propane. The same rules apply for naming but the prefix the prefix cyclo-cyclo- is added. is added.
Example:Example:
cyclopropane: Ccyclopropane: C33HH66CH2
CH2CH2
More examples: More examples:
Cyclobutane: CCyclobutane: C44HH88
CH2
CH2
CH2
CH2
1-ethyl1-ethyl--2-propyl2-propylcyclobutane
CH2
CH
CH
CH2
CH2 CH3
CH2 CH2 CH3
Properties of AlkanesProperties of Alkanes
Physical PropertiesPhysical Properties Nonpolar results in London Dispersion ForcesNonpolar 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 solidsC16 > wax like solids Fairly unreactive because saturated bonds are Fairly unreactive because saturated bonds are
strong (good for plastics, lubricants)strong (good for plastics, lubricants) RefiningRefining: physically separating HC mixtures (coal : physically separating HC mixtures (coal
and natural gas)and natural gas) Petroleum refiningPetroleum refining: boil petroleum and separate : boil petroleum and separate
on basis of boiling point (fractional distillation)on basis of boiling point (fractional distillation)
Properties of AlkanesProperties of Alkanes
Chemical PropertiesChemical Properties CrackingCracking – done to meet extra demand for – done to meet extra demand for
smaller alkanes (gasoline C5 – C12)smaller alkanes (gasoline C5 – C12) ThermalThermal cracking – cracking – high heat, no oxygenhigh heat, no oxygen CatalyticCatalytic crackingcracking – catalyst used, no oxygen – catalyst used, no oxygen
heat or catalystheat or catalyst
C17H36(s) + H2(g) C17H36(s) + H2(g) → → C9H20(l) + C8H18(l)C9H20(l) + C8H18(l)
Reforming – converts low grade gasoline Reforming – converts low grade gasoline into higher grade, makes synthetic into higher grade, makes synthetic lubricants and petrochemicalslubricants and petrochemicals
heat or catalystheat or catalyst
C5H12(l) + C5H12(l) C5H12(l) + C5H12(l) →→ C10H22(s) + H2(g) C10H22(s) + H2(g)
CombustionCombustion – burning of fuels, incomplete – burning of fuels, incomplete combustion forms CO(g)combustion forms CO(g)
C17H36(s) + O2(g) C17H36(s) + O2(g) →→ CO2(g) + H20(g)CO2(g) + H20(g)
SubstitutionSubstitution – reactions where one atom – reactions where one atom or group substitutes a H atomor group substitutes a H atom
CH4 + Cl2 CH4 + Cl2 →→ CH3Cl + HCl CH3Cl + HCl