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ORGANIC CHEMISTRY Organic Chemistry: The chemistry of carbon and carbon-based compounds Organic Chemistry in everyday life: Smells & tastes: fruits, chocolate, fish, mint Medications: Aspirin, Tylenol, Decongestants, Sedatives Addictive substances: Caffeine, Nicotine, Alcohol, Narcotics Hormones/Neurotransmitters: Adrenaline, Epinephrine Food/Nutrients: Carbohydrates, Protein, Fat, Vitamins Genetics: DNA, RNA Consumer products: Plastics, Nylon, Rayon, Polyester DRAWING ORGANIC STRUCTURES Shortcuts make structures easier & faster to draw Butane: C4H10 Lewis Structure H H H H H C C C C H H H H Carbon Atoms H Condensed Structures CH3 CH2 CH2 CH3 CH3CH2CH2CH3 CH3(CH2)2CH3 Line Structure • Only shows bonds • C atoms assumed at each end and intersection of bonds • H atoms not shown • Assume 4 bonds to each C • Fulfill C’s 4 bonds by adding H’s TYPES OF ORGANIC COMPOUNDS Classified according to functional group Alkane Alcohol Carboxylic acid O OH OH Alkene Ether Amine NH2 O Alkyne Ketone Amide O O NH2 Haloalkane Aldehyde Amino acid O O Cl Br H H2N OH BIG IDEA IN ORGANIC CHEMISTRY Structure controls Function Each functional group has predictable reactivity ALKANES OR PARAFFINS All C atoms are tetrahedral and sp3 hybridized (only C-C single bonds) General formula = CnH2n+2 (CH4, C2H6, C3H8, C4H10, etc.) Can have linear or branched alkanes CH3 C5H12 1° 3° H3C C CH2 CH3 H 2° • Same molecular formula, different structure: structural isomers • Branches are called substituents • Primary (1°) carbon atom: bound to one other C atom • Secondary (2°) C atom: bound to 2 other C atoms • Tertiary (3°) C atom: ” 3 ” • Quaternary (4°) C atom: ” 4 ” ISOMERS The fat dog shook himself, and then rolled over on the wet rug. OR The dog shook the fat rug, then rolled over and wet on himself. These two statements use the same words... but have very different meanings! Likewise, isomers may have the same formula, but have very different structures… STRUCTURAL ISOMERS OF C4H10 2-methylpropane or STRUCTURAL ISOMER PRACTICE On piece of your own paper, draw AND name ALL of the isomers for the following alkanes: Formulas Pentane C5H12 Hexane C6H14 Heptane C7H16 # isomers 3 5 9 Some of your drawings may look different, but they are only different structures (isomers) if they also have different names If you complete that, try to draw and name all of the isomers for octane (C8H18). There are 18 of them! STRUCTURAL ISOMERS: PENTANE (C5H12) pentane 2-methylbutane 2,2-dimethylpropane STRUCTURAL ISOMERS: HEXANE (C6H14) hexane 2,3-dimethylbutane 2-methylpentane 2,2-dimethylbutane 3-methylpentane STRUCTURAL ISOMERS: HEPTANE (C7H16) heptane 2,2-dimethylpentane 2-methylhexane 2,3-dimethylpentane 3-methylhexane STRUCTURAL ISOMERS: HEPTANE (C7H16) 2,4-dimethylpentane 3-ethylpentane 3,3-dimethylpentane 2,2,3-trimethylbutane COMPARING STRUCTURAL ISOMERS C5H12 Structure (Same formula, different structure) Name Boiling point (°C) pentane 36.0 2-methylbutane 27.9 2,2-dimethylpropane 9.5 More branching → weaker London dispersion forces BP/MP of Linear alkanes > BP/MP of branched alkanes NAMES OF LINEAR ALKANES AND ALKYL SUBSTITUENTS # of C atoms Alkane 1 CH4 2 CH3CH3 3 CH3CH2CH3 4 CH3CH2CH2CH3 Alkyl substituents Methane Ethane Propane Butane 5 Pentane 6 Hexane 7 Heptane 8 Octane 9 Nonane 10 Decane -CH3 -CH2CH3 -CH2CH2CH3 Methyl Ethyl Propyl etc. Root: number of C atoms Suffix: functional group (-ane for alkanes) (-yl for alkyl groups) H H H H H H C H H H H H H H Methane CH4 Butane C4H10 H H H H H R? C C C C H C H R ? C C C C H H H H H H Methyl -CH3 Butyl -C4H9 Where R = any other C atom or arrangement of C atoms FIRST TEN HYDROCARBONS: PROPERTIES Name Number of Carbon Atoms Molecular Formula Melting Point, oC Boiling Point, oC # of Isomers Methane 1 CH4 -182.5 -161.5 1 Ethane 2 C2H6 -183.2 -88.6 1 Propane 3 C3H8 -187.7 -42.1 1 Butane 4 C4H10 -138.3 -0.5 2 Pentane 5 C5H12 -129.7 36.1 3 Hexane 6 C6H14 -95.3 68.7 5 Heptane 7 C7H16 -90.6 98.4 9 Octane 8 C8H18 -56.8 125.7 18 Nonane 9 C9H20 -53.6 150.8 35 Decane 10 C10H22 -29.7 174.0 75 PROPERTIES OF ALKANES Nonpolar → only London Dispersion Forces IMF Larger molecular weight → Stronger London dispersion forces Compound Methane Formula CH4 MW 16 Boiling point (°C) -164 Ethane Propane Butane C2H6 C3H8 C4H10 30 44 58 -88.6 -42.1 -0.5 Pentane C5H12 72 +36.0 Linear Alkanes: 1 - 4 C atoms: gas at room temp 5 - 15 C atoms: liquid at room temp >15 C atoms: solid at room temp FRACTIONAL DISTILLATION OF CRUDE OIL Kelter, Carr, Scott, Chemistry A World of Choices 1999, page 429 NAMING BRANCHED ALKANES (IUPAC) 4-ethyl Octane 2 8 6 7 1. 5 4 3 4-ethyl-3,5-dimethyloctane 1 3-methyl and 5-methyl = 3,5-dimethyl Root name: name of longest continuous C chain (parent chain) • 2 equally long? Choose the one with more branches 2. Number C atoms in chain, starting at end with first branch 3. Identify substituents, give each a number (C it is connected to) • 4. List substituents alphabetically before root name • 5. Two or more identical substituents: use prefixes (di-, tri-, tetra-, etc.) Do not alphabetize prefixes Punctuation: commas separate numbers from each other hyphens separate numbers from names no space between last substituent & root name COMMON NAMES OF OTHER ALKYL SUBSTITUENTS Remember that R = any carbon chain R 3 carbons CH CH3 R CH3 isopropyl alphabetized as “i” “iso” indicates symmetry R CH2 CH CH3 R isobutyl CH3 4 carbons 2o R alphabetized as “i” CH CH2 CH3 R 2o CH3 sec-butyl alphabetized as “b” Secondary carbon CH3 R 3o C CH3 CH3 R 3o tert-butyl alphabetized as “b” Tertiary carbon NAMING PRACTICE Expanded Structure H H H Line Structure H H C C C C H H H H H C H H butane 2 - methylbutane NAMING PRACTICE H H CH3 H C C C 6 1 52 43 CH3 Line Structure H H C H 3 4 H C H 25 H C H 16 H 4,4-dimethylhexane 3,3-dimethylhexane Lowest sum of numbers is correct