24.1 Petroleum Refining and the Hydrocarbons24.2 Functional Groups and Organic Synthesis24.3 Pesticides and PharmaceuticalsChapter 24 From Petroleum toPharmaceuticalsPhysical Properties ofPhysical Properties ofAlkanes Alkanes andand Cycloalkanes CycloalkanesWhy do molecules tend to stick together?increase with increasing number of carbonsincrease with increasing number of carbonsmore atoms, more electrons, more more atoms, more electrons, more opportunities for induced dipole-inducedopportunities for induced dipole-induceddipole forces dipole forces decrease with chain branchingdecrease with chain branchingbranched molecules are more compact withbranched molecules are more compact withsmaller surface areasmaller surface area——fewer points of contactfewer points of contactwith other molecules with other molecules Boiling PointsBoiling PointsCH4n-C4H10n-C7H16n-C8H18n-C6H14Boiling points and melting points of n-alkanesincrease with increasing number of carbonsincrease with increasing number of carbonsmore atoms, more electrons, more more atoms, more electrons, more opportunities for induced dipole-inducedopportunities for induced dipole-induceddipole forces dipole forces Boiling PointsBoiling Points HeptaneHeptanebp bp 98°C98°C OctaneOctanebp bp 125°C125°C NonaneNonanebp bp 150°C150°CBoiling PointsBoiling Points n-octanen-octane:: bp bp 125°C125°C2-Methylheptane:2-Methylheptane: bp bp 118°C118°C 2,2,3,3-Tetramethylbutane:2,2,3,3-Tetramethylbutane: bp bp 107°C107°Cdecrease with chain branching (WHY?)decrease with chain branching (WHY?)branched molecules are more compact withbranched molecules are more compact withsmaller surface areasmaller surface area——fewer points of contactfewer points of contactwith other moleculeswith other moleculesBoiling Points ofBoiling Points of Alkanes Alkanesgoverned by strength of intermoleculargoverned by strength of intermolecularattractive forcesattractive forcesalkanes alkanes areare nonpolar nonpolar, so dipole-dipole and, so dipole-dipole anddipole-induced dipole forces are absentdipole-induced dipole forces are absentonly forces of intermolecular attraction areonly forces of intermolecular attraction areinduced dipole-induced dipole forcesinduced dipole-induced dipole forcesInduced dipole-Induced dipole attractive forcesInduced dipole-Induced dipole attractive forces++––++––twotwo nonpolar nonpolar moleculesmoleculescenter of positive charge and center of negativecenter of positive charge and center of negativecharge coincide in eachcharge coincide in eachInduced dipole-Induced dipole attractive forcesInduced dipole-Induced dipole attractive forces++––++––movement of electrons creates anmovement of electrons creates aninstantaneous dipole in one molecule (left)instantaneous dipole in one molecule (left)Induced dipole-Induced dipole attractive forcesInduced dipole-Induced dipole attractive forces++––++––temporary dipole in one molecule (left)temporary dipole in one molecule (left)induces a complementary dipole in otherinduces a complementary dipole in othermolecule (right)molecule (right)Induced dipole-Induced dipole attractive forcesInduced dipole-Induced dipole attractive forces++––++––temporary dipole in one molecule (left)temporary dipole in one molecule (left)induces a complementary dipole in otherinduces a complementary dipole in othermolecule (right)molecule (right)Induced dipole-Induced dipole attractive forcesInduced dipole-Induced dipole attractive forces++––++––the result is a small attractive force betweenthe result is a small attractive force betweenthe two moleculesthe two moleculesInduced dipole-Induced dipole attractive forcesInduced dipole-Induced dipole attractive forces++––++––the result is a small attractive force betweenthe result is a small attractive force betweenthe two moleculesthe two moleculesStraight chain hydrocarbonStraight chain hydrocarbonBranched hydrocarbonBranched hydrocarbonLots of intermolecularLots of intermolecularcontactscontactsFewer intermolecularFewer intermolecularcontactscontactsSmall organic molecules: required to sustain life and healthLife: food (pesticides and herbicides)Health: disease and pain control (pharmaceuticals)Large organic molecules: Polymers (many “mers” orrepeating units)Biomolecules: the blue print (DNA) and the machinery(proteins and sugars) of lifeOrganic short hand for structuresNote hydrocarbon skeleton, recognize functional groupsStructure of some small molecule analgesicsMolecular shape and functional groups determine theonset of pain and the molecular structure for its reliefStructure of some small molecule pesticidesKill insects indiscriminately. Also be toxic to humans.Structure of some small molecule herbicidesKill only insects; some attract insects and make them sterileStructure of some small molecule antibiotics andBacteria mistake molecule (a) for a molecule they needto make folic acid. This mistake kills them.Structure of some steroidsCholesterol is found in all tissues of the bodyHuman sex hormones are structurally based on