Organic Chemistry Hydrocarbons Organic Chemistry • The study of the compounds that contain the element carbon • Are numerous due to the bonding capability of carbon Carbon • Is able to form 4 covalent bonds • can form single, double, or triple covalent bonds • makes possible a large number of compounds Organic Compounds • Extensive in nature • more numerous than inorganic compounds Major sources of raw materials from which organic chemicals are obtained • Petroleum • coal • wood • animal sources Characteristics of organic compounds • Generally insoluble in water (are generally nonpolar) • dissolve in nonpolar solvents (benzene) – organic compounds that are somewhat polar will dissolve in water • Are generally nonelectrolytes • generally low melting points – nonpolar - intermolecular forces weak • slower reactions than those involving inorganic compounds – have strong covalent bonding within the molecule Bonding • Forms compounds by covalent bonding • C atom has 4 valence electrons forms 4 covalent bonds • are spacially directed toward the corners of a regular tetrahedron • | • —C— • | Can share electrons with other C atoms 2 adjacent C atoms can share 1,2, or 3 pairs of electrons compounds are molecular in structure covalent bond represent by “ — “ (bond line) represents one pair of shared electrons Types of formulas • STRUCTURAL FORMULA – Formula showing bonding • CONDENSED STRUCTURAL FORMULA – leave out some bonds and/or atoms from the structural formula • Page 746 • examples in table – – – – – molecular formula complete structural formula condensed structural formula more condensed structural formula carbon skeleton Isomers • Have same molecular formula but different structures • example – propanol CH3CH2CHO – acetone CH3COCH3 • both have molecular formula C3H6O • As the number of atoms in the molecule increases, the possibility of more spatial arrangements increases (more isomers) Saturated compounds • Organic compounds in which carbon atoms are bonded by the sharing of a single pair of electrons. Are all single bonds (one pair shared) • | | | | | • —C—C—C—C—C— • | | | | | Unsaturated compounds • Contain 2 adjacent carbon atoms bonded by the sharing of more than one pair of electrons • double bond > C = C < • triple bond — C = C — • (add third bond line please) Hydrocarbons • Organic compounds that contain only hydrogen and carbon Homologous series of hydrocarbons • Groups having related structures and properties • each member of a series differs from the one before it by a common amount • As members of a series increase in molecular size, boiling point and freezing point increases due to Van der Waal’s Forces (force that holds nonpolar molecules together) Alkanes • Series of saturated hydrocarbons having the general formula: • CnH2n+2 • also called methane series or paraffin series • Alkane series begins showing isomerism at butane (C4H10) • Straight-chain alkanes - contain any number of carbon atoms, one after another, in a chain • Page 745 • Must memorize the prefixes - tells you how many carbon atoms are in the compounds METHANE CH4 • • • • • • H | H—C—H | H ETHANE C2H6 • • • • • • H H | | H—C—C—H | | H H PROPANE C3H8 • • • • • H H H | | | H— C — C — C — H | | | H H H BUTANE C4H10 • • • • • H H H H | | | | H—C—C—C—C—H | | | | H H H H PENTANE C5H12 • • • • • H H H H H | | | | | H—C—C—C—C—C—H | | | | | H H H H H • Page 747 • Sample problem 25-1 (done for you) • Practice problems – change to six and seven carbons SUBSTITUENTS • An atom or group of atoms that can take the place of a hydrogen atom on a parent hydrocarbon molecule • The halogens and groups of atoms including C, H, O, N, S, or P may take the place of a hydrogen atoms • A hydrocarbon substituent is called an alkyl group can be one carbon or several carbons long • examples: • methyl CH3— • ethyl CH3CH2 — • propyl CH3CH2CH2 • Alkyl group consists of an alkane with one hydrogen removed • alkyl groups sometimes called radicals • Are named by removing the -ane ending from the parent hydrocarbon name and adding yl • page 748 Answer red dot question • Page 748-749 • branched chain alkane - alkane with one or more alkyl groups • IUPAC SYSTEM FOR NAMING BRANCHED CHAIN ALKANES • follow in text #1-6 • Page 749 Sample Problem 252 • Practice problem 3 • Page 750 Practice Problem 4 • Can also reconstruct the structural formula by following the rules on page 750 • Sample problem 25-3 • practice problem 5 • Pg. 751 Practice problem 6 Unsaturated hydrocarbons • ALKENES – contain one double bond between adjacent carbons • page 754 look at structures • Ethene (ethylene) • propene (propylene) • butene • pentene • and so on…….. Naming alkenes • Locate the longest chain that contains the double bond – that is the parent alkene • use that root name plus ene ending • number the chain so that the carbons with the double bond get the lowest numbers • Substituents names the same way as for alkanes • use a number to indicate the location of the carbon that has the double bond ALKYNES • Contain a triple bond between 2 carbons • not plentiful in nature • ethyne (acetylene) • page 753 look at table 25.2 Isomerism • Structural isomers – Compounds that have the same molecular formula but different molecular structures • examples on page 754 • butane and 2-methylpropane • Have different physical properties (melting point, boiling point) In general, the more highly branched in structure, the lower its boiling point) • also have different chemical properties Geometric isomers • Differ only in the geometry of their substituted groups • trans configuration - the substituted groups are on the opposite side of the double bond • Cis configuration - the substituted groups are on the same side of the double bond • example on pages 754-755 • answer pink question #2 Stereoisomers • Molecules of the same molecular structure that differ only in the arrangement of the atoms in space. • Page 755 example • page 756 samples and practice