Chapter 11 Organic Compounds Alkanes ORGANIC COMPOUNDS In

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Chapter 11 Organic Compounds: Alkanes

Chapter 11 Organic Compounds: Alkanes

ORGANIC COMPOUNDS • In 1828, Friedrich Wöhler first synthesized an organic compound from an

ORGANIC COMPOUNDS • In 1828, Friedrich Wöhler first synthesized an organic compound from an inorganic source. • This discredited the “vital force” theory.

ORGANIC CHEMISTRY • Organic chemistry • Inorganic chemistry • The principle components of food,

ORGANIC CHEMISTRY • Organic chemistry • Inorganic chemistry • The principle components of food, fuels, wood construction, and clothing are ________.

ORGANIC CHEMISTRY (continued) • An estimated 500, 000 _________ have been identified, but more

ORGANIC CHEMISTRY (continued) • An estimated 500, 000 _________ have been identified, but more than 9 million _________ are known, and thousands of new ones are synthesized or isolated each year.

HUND'S RULE

HUND'S RULE

BONDING CHARACTERISTICS

BONDING CHARACTERISTICS

ATOMIC ORBITALS

ATOMIC ORBITALS

BONDING CHARACTERISTICS (continued) • An sp 3 orbital has a two-lobed shape, similar to

BONDING CHARACTERISTICS (continued) • An sp 3 orbital has a two-lobed shape, similar to the shape of a _______ but with different-sized lobes. • Each carbon-hydrogen bond in methane arises from an overlap of a C ____ and an H _______ orbital. • The sharing of two electrons in this overlap region creates a _______

BONDING CHARACTERISTICS (continued) • The four hybrid sp 3 orbitals allow carbon to form

BONDING CHARACTERISTICS (continued) • The four hybrid sp 3 orbitals allow carbon to form ____ bonds. When carbon is joined to four substituents (______), the resultant configuration is _______ in shape.

BONDING CHARACTERISTICS (continued) • Carbon can also bond to other carbon atoms. • In

BONDING CHARACTERISTICS (continued) • Carbon can also bond to other carbon atoms. • In principle, there is no limit to the number of carbon atoms that can bond covalently. • Organic molecules range from the simple molecules like CH 4 to very complicated molecules containing over a million carbon atoms.

ISOMERISM • _______: Compounds that have identical molecular formulas, but different arrangement of atoms.

ISOMERISM • _______: Compounds that have identical molecular formulas, but different arrangement of atoms. • _________: A type of _______ in which the atoms bond in different patterns. • Isomers of C 2 H 6 O:

FUNCTIONAL GROUPS • __________are unique reactive combinations of atoms that differentiate organic compounds of

FUNCTIONAL GROUPS • __________are unique reactive combinations of atoms that differentiate organic compounds of one class from those of another. • Examples:

FUNCTIONAL GROUPS (continued)

FUNCTIONAL GROUPS (continued)

FUNCTIONAL GROUPS (continued)

FUNCTIONAL GROUPS (continued)

REPRESENTING ORGANIC COMPOUNDS • Expanded structural formulas • Condensed structural formulas

REPRESENTING ORGANIC COMPOUNDS • Expanded structural formulas • Condensed structural formulas

CLASSIFICATION OF HYDROCARBONS • _________ are organic compounds that contain only carbon and hydrogen.

CLASSIFICATION OF HYDROCARBONS • _________ are organic compounds that contain only carbon and hydrogen. • A ________ that contains only single bonds is a saturated hydrocarbon or ______. • Unsaturated hydrocarbons are called ________________ and contain double bonds, triple bonds, or ring systems with alternating double bonds.

CLASSIFICATION OF HYDROCARBONS (continued)

CLASSIFICATION OF HYDROCARBONS (continued)

ALKANES • Alkanes can be represented by the general formula Cn. H 2 n+2,

ALKANES • Alkanes can be represented by the general formula Cn. H 2 n+2, where the n is the number of carbon atoms in the molecule. • The simplest alkane is _________, which is the primary compound in natural gas.

ALKANES (continued) • More complex alkanes can be C—C—C C | C—C—C | C

ALKANES (continued) • More complex alkanes can be C—C—C C | C—C—C | C

ALKANES (continued)

ALKANES (continued)

CONFORMATIONS OF ALKANES • . • The different arrangements of atoms in space achieved

CONFORMATIONS OF ALKANES • . • The different arrangements of atoms in space achieved by rotation about single bonds are called _______.

CONFORMATIONS OF ALKANES (continued) • This figure shows perspective models and carbon skeletons of

CONFORMATIONS OF ALKANES (continued) • This figure shows perspective models and carbon skeletons of two conformations of n-butane.

CONFORMATIONS OF ALKANES (continued) • Which of the following pairs represent structural isomers, and

CONFORMATIONS OF ALKANES (continued) • Which of the following pairs represent structural isomers, and which are simply the same compound? • Which are normal alkanes and which are branched alkanes?

CONFORMATIONS OF ALKANES (continued)

CONFORMATIONS OF ALKANES (continued)

CONFORMATIONS OF ALKANES (continued)

CONFORMATIONS OF ALKANES (continued)

ALKYL GROUPS • An alkyl group is a group differing by one hydrogen from

ALKYL GROUPS • An alkyl group is a group differing by one hydrogen from an alkane.

COMMON NONALKYL GROUPS

COMMON NONALKYL GROUPS

NAMING ALKANES • The IUPAC method consists of: Root

NAMING ALKANES • The IUPAC method consists of: Root

NAMING ALKANES (continued) • Step 1: Identify and name the longest carbon chain. This

NAMING ALKANES (continued) • Step 1: Identify and name the longest carbon chain. This gives the root and ending. (The ending –ane signifies the alkane family. ) • Step 2: Number the longest carbon chain to give the lowest number to any carbon to which a group is attached. 5 CH CH 3 | | Example: CH 2 — CH 3 (pentane) 4 3 3 2 1 • Step 3: Locate and name the attached alkyl groups. • Step 4: Combine the longest chain and the branches into the name. 2 -methylpentane

NAMING ALKANES (continued) • Step 5: • For multiple branches, show the location of

NAMING ALKANES (continued) • Step 5: • For multiple branches, show the location of each branch with numbers. • For multiple branches of the same type, modify the name with di-, tri-, tetra-, penta-, etc. and separate the position numbers by commas. • List multiple branches alphabetically. Ignore the di-, tri-, sec-, and t- prefixes. Example: 1 CH 3— 2 CH — 3 CH — 4 CH — 5 CH 2 — 6 CH 2 — 7 CH 3 | | | CH 3 CH–CH 3 | CH 3 4 -isopropyl-2, 3 -dimethylheptane

THE SHAPE OF CYCLOALKANES

THE SHAPE OF CYCLOALKANES

THE SHAPE OF CYCLOALKANES (continued)

THE SHAPE OF CYCLOALKANES (continued)

NAMING CYCLOALKANES • Cycloalkanes are alkanes containing rings of carbon atoms. • The prefix

NAMING CYCLOALKANES • Cycloalkanes are alkanes containing rings of carbon atoms. • The prefix cyclo- is used before the alkane name. • When two or more substituents are attached to the cycloalkanes, the ring numbering begins with the first group alphabetically and proceeds to give lowest numbers possible. Example: CH 2 CH 3 1 CH 3 3 2 1 -ethyl-3 -methylcyclopentane

ISOMERISM & CYCLOALKANES • Stereoisomers are compounds with the same structural formula but different

ISOMERISM & CYCLOALKANES • Stereoisomers are compounds with the same structural formula but different spatial arrangements of atoms. • Geometric isomers are molecules with restricted rotation around C-C bonds that differ in the three-dimensional arrangements of their atoms in space and not in the order of linkage of atoms. • Rotation about C-C single bonds occurs in open-chain compounds but not within rings.

ISOMERISM & CYCLOALKANES (continued) • Two geometric isomers exist for 1, 2 -dimethylcyclopentane. •

ISOMERISM & CYCLOALKANES (continued) • Two geometric isomers exist for 1, 2 -dimethylcyclopentane. • Cis-substituents are on the same side of the ring. • Trans-substituents are on the opposite sides of the ring.

PHYSICAL PROPERTIES OF ALKANES • • • Non-polar molecules with weak intermolecular forces Not

PHYSICAL PROPERTIES OF ALKANES • • • Non-polar molecules with weak intermolecular forces Not soluble in water (hydrophobic) Low density (less dense than water) Melting points increase with molecular size Boiling points increase with molecular size

PHYSICAL PROPERTIES OF ALKANES (continued) • A homologous series is a group of compounds

PHYSICAL PROPERTIES OF ALKANES (continued) • A homologous series is a group of compounds with the same functional class that differ by a –CH 2– group.

PHYSICAL PROPERTIES OF ALKANES (continued)

PHYSICAL PROPERTIES OF ALKANES (continued)

ALKANE REACTIONS • Alkanes are the least reactive of all organic compounds. • The

ALKANE REACTIONS • Alkanes are the least reactive of all organic compounds. • The most significant reaction of alkanes is combustion (rapid oxidation). • Many alkanes are used as fuels. • Methane – natural gas • Propane – used in gas grills • Butane – lighters • Gasoline – a mixture of hydrocarbons

ALKANE REACTIONS (continued) • Complete Combustion (in the presence of adequate oxygen) CH 4

ALKANE REACTIONS (continued) • Complete Combustion (in the presence of adequate oxygen) CH 4 + 2 O 2 → CO 2 + 2 H 2 O + 212. 8 kcal/mol • Incomplete Combustion (not enough oxygen available) 2 CH 4 + 3 O 2 → 2 CO + 4 H 2 O CH 4 + O 2 → C + 2 H 2 O