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 –F–Formula showing bonding CONDENSED STRUCTURAL FORMULA –l–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 CH 3 CH 2 CHO –acetone CH 3 COCH 3 both have molecular formula C 3 H 6 O

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: C n H 2n+2 also called methane series or paraffin series

Alkane series begins showing isomerism at butane (C 4 H 10 ) 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 CH 4 H | H — C — H | H

ETHANE C 2 H 6 H H | | H — C — C — H | | H H

PROPANE C 3 H 8 H H H | | | H— C — C — C — H | | | H H H

BUTANE C 4 H 10 H H H H | | | | H — C — C — C — C — H | | | | H H H H

PENTANE C 5 H 12 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 CH 3 — ethyl CH 3 CH 2 — propyl CH 3 CH 2 CH 2

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 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 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 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