Organic Chemistry. Chapter 3 Saturated Hydrocarbons

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1 Organic Chemistry Organic Chemistry Chapter 3 Saturated Hydrocarbons Organic Chemistry is an entire branch of chemistry because carbon can 1) 2) 3) Vital Force Theory origination of organic term 3.1 Molecular and Structural Formulas Molecular formula Structural formula Combining power Lewis Dot Combining Element Structure Power 3.2 Families of Organic Compounds Families/Classes <<see table 3.2 pg. 71>> hydrocarbons saturated unsaturated 1

2 3.3 Alkanes obtained from (w/ other hydrocarbons) Important Uses 1) 2) General formula: Formulas and Properties of Normal Alkanes <<see table 3.3 pg. 73>> Ball and Stick vs. Space-filling models <<see fig. 3-2 pg. 74>> Alkane bonding features 1) carbon is valent 2) carbon has geometry VSEPR Theory Overview electron groups are as far away from one another as possible and thus experience the least amount of repulsion. 2 electron groups 3 electron groups 4 electron groups Build a butane Molecule Conformations and single-bond free rotation <<See fig 3.6 see pg. 77>> The conformation that is favored determines 2

3 3.4 Types of Structural Formulas Expanded condensed line Structural structural structure Formula formula Partly expanded structural formula 3.5 Constitutional Isomers of Alkanes Isomers Constitutional Geometric 3.6 Naming Alkanes Types C-atoms 1, 2, 3, 4 Naming Use IUPAC System (end in ane) # Molecular Structural Skeletal line Isomers # C s Formula formula structure structure Straight chain alkanes are normal alkanes 3

4 Alkyl groups Build methane Build ethane Other groups F- Cl- Br- I- -NO 2 -NH 2 -OH Build propane Build butane Build isobutane (2-methylpropane) <<Practice Naming See Naming Packet>> IUPAC Nomenclature Alkanes 1) Name of longest chain becomes base/parent name Suffix of the family name is added to the end of the base/parent name 2) Substituents/groups must be named a. names of alkyl groups placed in front of base name b. Use prefixes di, tri, tetra etc. to indicate # of each group c. alphabetize names of alkyl groups (ignore all prefixes except iso ) 3) Number carbons in parent chain so groups will result in the lowest sum (usually means # on side w/ nearest branch) 4) In front of the name of each alkyl group, place the number of the carbon to which each group is attached. 5) Use hyphens to separate # s from words; use commas to separate # s 4

5 3.7 Cycloalkanes General formula: Naming 1) Add cycle to straight-chain name 2) # C s so lowest set of # s (don t need 1- if only one substituent) 3.8 cis-trans Stereoisomerism in cycloalkanes (isomers see section 3.5) Build 1,2-dimethylcyclopropane 3.9 Physical Properties of Alkanes and Cycloalkanes physical properties correlate with the strength of a compounds secondary forces Need a review of molecular interactions/secondary forces 1.8 Molecular Interactions & 1.9 Secondary Forces Ionic Compounds Molecular Compounds 1) London Dispersion Forces Types of Intermolecular Forces 2) Dipole-dipole forces 3) Hydrogen bonding <<see table 1.10 pg. 32>> 5

6 3.9 Physical Properties of Alkanes and Cycloalkanes - AGAIN physical properties correlate with the strength of a compounds secondary forces Alkanes are non-polar molecules and thus have forces. 1) melting point/boiling point < 30 C C 1 C 4 gases C C 5 C 10 gasoline fuel C C 10 C 18 kerosene and jet fuel C C 15 C 18 diesel fuel & heating oil C C 17 C 25 lubricating & mineral oils > 400 C C 20 C 40 paraffin wax, asphalt a. as molar mass increases, m.p./b.p. b. If ~ same molar mass, shape determines m.p./b.p. build: cyclobutane butane 2-methylpropane 2) Density As secondary forces increase, density. 3) Solubility If two substances have similar IMF, they will dissolve in one another. Alkanes are non-polar thus dissolve in water dissolve in benzene (C 6 H 6 ) 3.10 Chemical Properties of Alkanes and Cycloalkanes Saturated hydrocarbons have reactivity relative to other families. e.g. They are inert to: strong acids/strong bases reducing agents (ex. H 2 ) most oxidizing agents (ex. KMnO 4, K 2 Cr 2 O 7 ) Combustion - oxidation reaction Inorganic definition: oxidation reduction Organic definition: oxidation reduction 6

7 In general: Incomplete combustion yields Bad because 1) 2) In our bodies food stuffs are oxidized (calories are burned ) in an indirect way but it still: Food + O 2 CO 2 + H 2 O + energy Halogenation (Halogen substitution) In general: Greenhouse Effect (pg. 99) When gases are to incoming visible light, yet to the energy radiated from Earth. Greenhouse gases include: These gases and to one another which keeps heat near the Earth s surface. Why can burning fossil fuels be bad? Alkyl Halide Applications Freon dichlorodifluoromethane (CFC) Uses: Ozone Depletion Rxn: 7