Organic Chemistry

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 hydrogenand carbon

Homologous series of hydrocarbons • Groups having related structures and properties • each member of a series differs from the one before it by acommonamount

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

METHANECH4 • H • | • H — C — H • | • H

ETHANE C2H6 • H H • | | • H — C — C — 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 carbonslong

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 25-2 • 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 lowestnumbers

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 sideof 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

Organic Chemistry