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Hydrocarbon Names. Saturated hydrocarbons (alkanes) have general formula C n H 2n+2. CH 4 methane C 2 H 6 ethane C 3 H 8 propane C 4 H 10 butane C 5 H 12 pentane. C 6 H 14 hexane C 7 H 16 heptane C 8 H 18 octane C 9 H 20 nonane C 10 H 22 decane.
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Hydrocarbon Names • Saturated hydrocarbons (alkanes) have general formula CnH2n+2 • CH4 methane • C2H6 ethane • C3H8 propane • C4H10 butane • C5H12 pentane • C6H14 hexane • C7H16 heptane • C8H18 octane • C9H20 nonane • C10H22 decane Nonpolar bonds, only London dispersion forces
Acid Names • All acid formulas start with H • Binary acid names start with “hydro”, change root ending to “ic” and add “acid”. • HCl hydrochloric acid • HCN hydrocyanic acid • HBr • HI
Acid Names • Binary acids are only named as acids when in water solution. • Dry compounds are named as molecular compounds • Example: HCl is hydrochloric acid in water solution, but hydrogen chloride as a free gas
Ternary acid names • Use root of anion name followed by “-ic” or “-ous” and “acid” • “-ic” is used with anions ending in “-ate” and “-ous” is used for “-ite”. • H2SO4 sulfuric acid • H3PO4 • HNO3 • HClO2
Exceptions to Octet rule • Odd electron molecules (ex. NO2) • Electron deficient molecules (ex. BF3) • Expanded octet - only for period 3 and higher (ex. SF6, PCl5, SO4-2)
Bond Polarity • Bonds are polar when there is an unequal distribution of electrons in a bond
Bond Polarity • Polar bonds are formed when two atoms of unequal electronegativity are bonded • The bond has a “dipole moment” because of the d+ and d- poles
Bond polarity • EN difference of 0-0.4: nonpolar covalent • EN difference of >0.4-1.4: polar covalent • EN difference of >1.4: ionic bond • Greater dipole-dipole interactions means greater mp and bp • Example: propane (C3H8, 44amu) has boiling point -42ºC, dimethyl ether (CH3OCH3, 46amu) has bp -23ºC
Molecular geometry • VSEPR = valence shell electron pair repulsion • Bonding and nonbonding pairs will arrange themselves around an atom so that they are as far from each other as possible • 2 pairs - BeCl2 • Linear geometry, bond angle = 180º
Molecular geometry • Three pairs - BH3, CH2O • Trigonal planar geometry, bond angle 120º • Four pairs - CH4 • Tetrahedral geometry, bond angle = 109.5º • Five pairs - PCl5 (expanded octet) • Trigonal bipyramid geometry, bond angles = 120º and 90º
Molecular geometry • Six pairs - SF6 • Octahedral geometry, bond angles 90º Nonbonding Pairs • Two bonding, one nonbonding - NO2- • Bent geometry (anything with two bonding pairs and at least one nonbonding pair) • Bond angle <120º, since nonbonding pair is larger
Molecular geometry • Three bonding, one nonbonding (NH3) • Trigonal pyramidal geometry, <109.5º bond angle Hybridization • Recombination of s and p orbitals to produce equivalent bonding orbitals • Two atoms and/or lone pairs: sp hybridization
Hybridization • Three atoms and/or lone pr.: sp2 • Four atoms and/or lone pr.: sp3