Chapter 3: Alkanes and Cycloalkanes - Learning Objectives and Structures - Prof. Cheng-Wei, Study notes of Organic Chemistry

Download Chapter 3: Alkanes and Cycloalkanes - Learning Objectives and Structures - Prof. Cheng-Wei and more Study notes Organic Chemistry in PDF only on Docsity! 1 Chapter 3. Alkanes and Cycloalkanes Learning objectives: 1. Name alkanes and cycloalkanes. 2. Write the structures of constitutional (or structural) isomers of alkanes. 3. Draw Newman projections of alkanes in staggered and eclipsed conformations, and arrange the order of stability for these conformations (conformational isomers). 4. Identify cis and trans relationship for the substituents on cycloalkanes. 5. Draw chair conformation of cyclohexane with unambiguous representation of axial and equatorial substituents. 6. Complete the equilibrium of two chair conformational isomers for a substituted cyclohexane, indicate the change for the relative positions of axial and equatorial substituents, and reason the stability between these two isomers. 7. Write the balanced equation for the combustion of alkanes. Molecular model kit will be very helpful for learning the material in this chapter. Sections to be covered (in the order of delivery): 3.1 Introduction # 3.2 Structure of Alkanes 3.3 Constitutional Isomerism in Alkanes 3.4 Nomenclature of Alkanes 3.5 Cycloalkanes 3.6 The IUPAC system - A general System of Nomenclature 3.7 Conformations of Alkanes and Cycloalkanes * 3.8 Cis - Trans Isomerism in Cycloalkanes * 3.9 Physical Properties of Alkanes and Cycloalkanes 3.10 Reactions of Alkanes 3.11 Sources of Alkanes # * Sections that will be focused # Sections that will be skipped Recommended additional problems 3.12 - 3.42, 3.48 - 3.52 2 3.2 Structure of Alkanes (i) Methane CH4 H C H H H H C H HH (ii) Ethane C2H6 H C H C H H C C H H H H H H H H H3C CH3 (iii) Butane C4H10 C H C H H H HH C H C H H H CH3CH2CH2CH3 => vi) : (vii) % (viii) : Gx) 4 > x) 4 > xi) "  6 B. Common Names Butyl groups (n-, iso-, sec-, tert-) C. Classification of Carbon and Hydrogen Atoms 3.5 Cycloalkanes General formula: CnH2n 7 3.6 The IUPAC system - A general System of Nomenclature Important infix Infix Nature of Carbon-carbon Bonds in the Main Chain Example -an- All single (saturated) bond H3C CH3 Ethane -en- One or more double bonds C C H H H H Ethene (ethylene) -yn- One or more triple bonds C CH H Ethyne (acetylene) Important suffix Suffix Class of Compound Example -e hydrocarbon CH3CH2CH2CH2CH3 Pentane -ol alcohol CH3CH2OH Ethanol -al aldehyde H3C C O H CH3CHO acetaldehyde -one ketone H3C C O CH3 CH3COCH3 acetone -oic acid carboxylic acid H3C C O OH CH3CO2H acetic acid 3.7 Conformations of Alkanes and Cycloalkanes Conformation: result of single bond rotation Conformational isomer: same atomic connectivity but different spatial arrangements of atoms. H C C H H H H H H C C H H H H H I II I II 10 1,3-diaxial interaction (diaxial interaction, axial-axial interaction) H H H H H C H H H C H H HH H H H H 11 3.8 Cis - Trans Isomerism in Cycloalkanes CH3 H H H3C H H H H H H H CH3 H H3C H H H H H H H H H H H3C H3C H H H H CH3 H3C 12 3.9 Physical Properties of Alkanes and Cycloalkanes A. Boiling Points Boiling points of alkanes increase with increasing molecule weight. B. Dispersion Forces and Interactions between Alkane Molecules Dispersion force (van der Waals interaction, electrostatic attraction)