Unformatted text preview: The Chemistry of Life: Organic and Biological Chemistry BLB 10th Chapter 25 25.1 General Characteristics Structure Carbon atoms form 4 bonds. Backbone consists of C--C-- chains or rings. C--H bond is nearly nonpolar. Stabilities C forms strong bonds with other elements. Alkanes are stable (unreactive). Functional groups (sect. 5) change reactivity. General Characteristics Solubility and acid-base properties Hydrocarbons: nonpolar, neutral soluble in water? ______ C--H (hydrocarbons) plus functional groups... -C--O--H polar, slightly acidic (alcohols) -C--O--O--H acidic (carboxylic acids) -C--N--R3 basic (amines) Surfactants combine both properties 25.2 Hydrocarbons Compounds containing only C and H Types: Alkanes (saturated) single C--C bonds Alkenes (unsaturated) double C--C bonds Alkynes (unsaturated) triple C--C bonds Aromatic alternating single and double bonds 25.3 Alkanes (CnH2n+2) Variations Unbranched (normal, straight-chained) Branched Cyclic Structural isomers same number and type of atoms but different bonding arrangements Tetrahedral geometry 3-D Arrangement Name Formula MM m.p. ( C) b.p. ( C) # isomers methane ethane propane butane CH4 C2H6 C3H8 C4H10 16 30 44 58 -183 -183 -187 -138 -161 -89 -44 -0.5 1 1 1 2 pentane hexane heptane octane C5H12 C6H14 C7H16 C8H18 72 86 100 114 -130 -95 -91 -57 36 68 98 125 3 5 9 18 nonane decane C9H20 C10H22 128 142 -54 -30 151 175 35 75 Butane Isomers Pentane Isomers Nomenclature Identify longest C chain base name 2. Number C atoms lowest number nearest substituent 3. Give position and name substituents. 4. More than one substituent? 1. Alphabetical Prefixes Some substituents have common names (Table 25.2, p. 1071) Structure & Nomenclature Examples Structure & Nomenclature Examples Structure & Nomenclature Examples Cycloalkanes (CnH2n) most stable structure stable structure strained & unstable 25.4 Alkenes & Alkynes Alkenes: C=C double bonds Named similarly with an ene ending and give position of double bond More reactive than alkanes Different arrangements of substituents may result in geometric isomers. Geometric isomers same atoms, same bonds, but different spatial arrangement of substituent groups. cis- and trans- Structural isomers Geometric isomers Structure & Nomenclature Examples Structure & Nomenclature Examples Alkenes & Alkynes Alkynes: C C triple bonds Named similarly with an yne ending and give position of triple bond More reactive than alkenes Aromatic Hydrocarbons Cyclic unsaturated hydrocarbons with alternating single and double C--C bonds. Ring system often has common name. Less reactive than alkenes or alkynes Bonding in Benzene 25.5 & 25.6 Functional Groups Site of reactivity R, R', R" represent the alkyl (hydrocarbon) group(s) to which functional group is attached. Functional Group examples Aspartame Functional Group examples H H NH2 O N CH2 CH CO2H HO H 25.7 Chirality Chiral compounds compounds containing carbons with four different attached groups Examples: CHFClBr, CH3--C--CH2CH2CH3 Enantiomers nonsuperimposable mirror images Enantiomers Enantiomers Chiral Compounds D- sugars are preferred L- amino acids are preferred Drugs Ibuprofen: one effective, other inactive Naproxen: one effective, other toxic ...
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- Spring '08