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Mary J. Bojan Chem 110 Organic Part 2 Hydrocarbons 1. Alkanes: all single bonds 2. Alkenes: C=C saturated v. unsaturated structural isomers geometric isomers 3. Alkynes: C≡C 4. Aromatic hydrocarbons Reactivity of hydrocarbons • addition reactions • combustion reactions Petroleum 1Mary J. Bojan Chem 110 Hydrocarbons This is the structure of 4-ethyl-2,3,3-trimethylnonane What is the molecular formula of this compound? How many ⎯CH3 groups are there on this compound? 2Mary J. Bojan Chem 110 HYDROCARBONS Simplest organic compounds Contain only C and H Alkanes saturated have the maximum number of H attached to the C skeleton. Alkenes unsaturated Alkynes have double or Aromatic triple bonds 3Mary J. Bojan Chem 110 ALKENES Contain one or more double bonds The C=C⎯H or C=C⎯C angle is 120° CnH2n Rotation about double bond is restricted propene ethene (ethylene) C CCHHHHC4 CHHHCH3CMary J. Bojan Chem 110 Butene C4H8 There are several possible structures for a chain of 4 carbons with one double bond. 1-butene 2-methylpropene 2-butene cis-2-butene trans-2-butene 5Mary J. Bojan Chem 110 Structural isomers: same molecular formula: different structure 1-butene 2-methylpropene 2-butene Structural vs. Geometric 6 Geometric isomers same molecular formula: different geometry cis-2-butene trans-2-butene cis-isomer: same side trans-isomer: opposite side (across)Mary J. Bojan Chem 110 ALKYNES: CnH2n-2 Contain ⎯C≡C⎯ H⎯C≡C⎯H CH3⎯C≡C⎯H ethyne propyne (acetylene) bond angle is 180° structural isomers no geometric isomers are possible 7 C C HCHHCHHHC C CCHHHHHH1-butyne 2-butyneMary J. Bojan Chem 110 Reactions of Alkenes and Alkynes Addition reaction – Double and triple bonds are reactive: addition reactions typically occur at room temperature. 8 For Alkenes CH3⎯CH=CH2 + Br2 → or CH3⎯CH=CH⎯CH3 + HX → where X = Cl, Br, I, OH, etc. For Alkynes CH3 ⎯C≡CH + 2Br2 → CH3-C ≡C -CH3 + 2HCl →Mary J. Bojan Chem 110 Aromatic Hydrocarbons Contain alternating single and double C-C Bonds Benzene is prototypical molecule Usually written: Aromatic hydrocarbons are less reactive than alkenes: Special kind of bonding Have “delocalized” π electrons Results in added stability 9 CCCCCCHHHHHH CCCCCCHHHHHHMary J. Bojan Chem 110 Reactivity of Hydrocarbons Same reaction: hydrocarbon + Br2 Colorless red 10 CH3ALKANE Heptane + Br2 ⎯→ ALKENE (and ALKYNES) 2-pentene + Br2 ⎯→ AROMATIC toluene + Br2 ⎯→Mary J. Bojan Chem 110 Functional Group classes Contain a representative group of elements in a fixed pattern Have similarities in structure and function (reactivity). 11 Seemingly small changes in structure can have big affect on molecular properties Functional Group Type hydrocarbon alcohol ether CH3⎯CH2⎯H CH3⎯CH2⎯OH CH3⎯O⎯CH3 ethane ethanol di-methyl ether gas liquid gas bp –89°C bp 78°C bp –24 °C water soluble Example: adding an oxygen changes a hydrocarbon into an alcohol or an ether…Mary J. Bojan Chem 110 Functional Group Classes Contain a representative group of elements in a fixed pattern: Each class has similarities in structure and function (reactivity). 12 Groups which have a carbonyl Aldehydes Ketones (R,R’≠H) Alcohols R-OH R≠H R = alkyl group Ethers R-O-R’ R,R’≠H Amines N HHRN R'HRN R'RR"CORCHOR'CROCarboxylic Ester Amide Acid OHCROOR'CRONHR'CROMary J. Bojan Chem 110 Functional Groups with O and N Alcohols R⎯OH hydroxyl group hydrocarbon (alkyl) group Ether R⎯O⎯R’ 13 N HHRN R'HRN R'RR"AminesMary J. Bojan Chem 110 Functional Groups Containing the carbonyl group Aldehyde Ketone Carboxylic Acids ⎯COOH 14 CORCHOR'CROOHCROMary J. Bojan Chem 110 Organic Acids and Bases AMINES weak bases, organic bases (like NH3) (CH3)3N(aq) + H+(aq) (CH3)3NH+(aq) CARBOXYLIC ACIDS weak acids, organic acids (aq) (aq) + H+(aq) 15 HOCRO-OCROMary J. Bojan Chem 110 Questions Which of the following hydrocarbon classes does NOT have a double or triple bond? 1 alkane 2 alkene 3 alkyne 4 aromatic Which one of the following functional group classes does not have a double bond? 1 aldehyde 2 Ketone 3 amine 5 ester 16Mary J. Bojan Chem 110 The presence and properties of functional groups are responsible for the action of drugs. What functional groups are present in these molecules? Acetyl salicylic acid Acetaminophen Ibuprofen 17 COO COOHCH3HO NHCOCH3CH3OOHH3CCH3Mary J. Bojan Chem 110 What’s Next? • Formulas tell us how atoms are connected to each other • Lewis structures tell us where the electrons are. QUESTIONS • What are the shapes of these molecules? • Can we use information about bonding, connectivity of atoms, molecular formulas, etc. to predict the shapes (and properties) of molecules?


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PSU CHEM 110 - Organic Part 2

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