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 Carbon Atoms 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 Condensed Structures CH3CH2CH2CH3 CH3(CH2)2CH3

Types of Organic Compounds Classified according to functional group Alkane Alkene Alkyne Haloalkane Alcohol Ether Ketone Aldehyde Carboxylic acid Amine Amino acid Amide

Big Idea in Organic Chemistry Structure controls Function Each functional group has predictable reactivity

Alkanes 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 C5H12 1° 3° 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 ”

Names of Linear Alkanes and Alkyl Substituents C atoms Alkane Alkyl substituents 1 2 3 4 5 6 7 8 9 10 CH4 CH3CH3 CH3CH2CH3 CH3CH2CH2CH3 Methane Ethane Propane Butane Pentane Hexane Heptane Octane Nonane Decane -CH3 -CH2CH3 -CH2CH2CH3 Methyl Ethyl Propyl etc. Root: number of C atoms Suffix: functional group (-ane for alkanes) (-yl for alkyl groups)

Naming Branched Alkanes (IUPAC) Octane 4-ethyl 6 2 8 4-ethyl-3,5-dimethyloctane 5 4 7 3 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 Number C atoms in chain, starting at end with first branch Identify substituents, give each a number (C it is connected to) Two or more identical substituents: use prefixes (di-, tri-, tetra-, etc.) List substituents alphabetically after prefix Do not alphabetize prefixes Punctuation: commas separate numbers from each other hyphens separate numbers from names no space between last substituent & root name

H C C H Methane CH4 Butane C4H10 H C ? C H ? R R Methyl -CH3 Butyl -C4H9 Where R = any other C atom or arrangement of C atoms

Naming Practice C H 2 - methylbutane butane Expanded Structure Line Structure H C 2 - methylbutane butane

Naming Practice H H CH3 H C C C H H C H H C H H C H H 4,4-dimethyl Line Structure 1 2 3 4 5 6 1 2 3 4 5 6 H H C H H C H H C H H 4,4-dimethyl hexane 3,3-dimethyl hexane Lowest sum of numbers is correct

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 # isomers Pentane Hexane Heptane C5H12 C6H14 C7H16 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) 2-methylbutane 2,2-dimethylpropane

Structural Isomers: Hexane (C6H14) 2,3-dimethylbutane 2-methylpentane 2,2-dimethylbutane 3-methylpentane

Structural Isomers: Heptane (C7H16) 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 (Same formula, different structure) C5H12 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

First Ten Hydrocarbons: Properties Number of Carbon Atoms Molecular Formula Melting Point, oC Boiling Point, oC # of Isomers Name Methane Ethane Propane Butane Pentane Hexane Heptane Octane Nonane Decane 1 2 3 4 5 6 7 8 9 10 CH4 C2H6 C3H8 C4H10 C5H12 C6H14 C7H16 C8H18 C9H20 C10H22 -182.5 -183.2 -187.7 -138.3 -129.7 95.3 90.6 56.8 53.6 29.7 -161.5 -88.6 -42.1 -0.5 36.1 68.7 98.4 125.7 150.8 174.0 1 2 3 5 9 18 35 75

First Ten Hydrocarbons: Properties As number of carbons increases, The boiling point increases The melting point increases The number of isomers increases

Nonpolar → only London Dispersion Forces Properties of Alkanes Nonpolar → only London Dispersion Forces Larger molecular weight → Stronger London dispersion forces Compound Methane Ethane Propane Butane Pentane Formula CH4 C2H6 C3H8 C4H10 C5H12 MW 16 30 44 58 72 Boiling point (°C) -164 -88.6 -42.1 -0.5 +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

Cycloalkanes Alkanes with closed ring(s) of C atoms General formula: CnH2n (C3H6, C4H8, C5H10, etc.) Naming: use cyclo- prefix before alkane name cyclopropane n = 3 cyclobutane n = 4 cyclopentane n = 5 cyclohexane n = 6 C3H6 C4H8 C5H10 C6H12 Not Stable Not Stable Not Stable Stable!!! Angles of the bonds need to be near 108 degrees and the first 3 do not have that.

Nomenclature of Cycloalkanes Find the longest carbon chain If it is in the cycloalkane – use it as the base name If it is in a straight chain, the cycloalkane becomes an alkyl group 1-cyclopropylpentane Name the alkyl groups coming off of the cycloalkane If there is only one, numbering is not needed If there are 2 or more alkyl groups Place the highest alphabetical alkyl group on the 1st carbon then followed by the others. In numbering the carbons, you want the sum of the numbers to be the least possible.

Nomenclature of Cycloalkanes Examples:

Nomenclature of Cycloalkanes Examples

Nomenclature of Cycloalkanes Examples

Nomenclature of Cycloalkanes Examples

Nomenclature of Cycloalkanes Examples

Chemical Bingo: Naming Review There are 28 structures or names drawn on the next slide. Select 24 of them to be placed on your bingo card. (free space) Because of space issues, I would number each bingo square and then list the names or structures on a separate sheet of paper If I give you a name, you must match it to a structure. If I give you a structure, you must match it to a name

Chemical Bingo: Alkanes isopropyl sec-butyl tert-butyl isobutyl decane nonane 2,3,4,5-tetramethylhexane 3,4-diethylhexane 3,5-diethyl-4-isopropylheptane 4-tert-butyl-3,5-dimethylheptane 4-ethyl-2,2,3,5,6,6-hexamethylheptane Any isomer of C5H12 Any isomer of C6H14 Any isomer of C7H16

16. ethane 17. cycloheptane 18. decane 19. 2,3,4,5-tetramethylhexane 20. 3,4-diethylhexane 21. 3,5-diethyl-4-propylheptane 22. 3,5-dimethyl-4-propylheptane 23. 4-ethyl-2,2,3,5,6,6-hexamethylheptane 24. 1-chloro-2-iodobutane 25. 1,2-diethylcyclohexane 26. 2-iodo-3,4-dimethylnonane 27. 3,3-diethyloctane 28. pentane