CHAPTER 17 Organic Chemistry 17.1 Hydrocarbon Molecules

Carbon can form covalent bonds with itself and create networks No other element has this ability

Carbon Diamond Each carbon atom can make four single bonds and form a tetrahedral structure Tetrahedral structure Diamond has a tetrahedral lattice, and it is the hardest substance known to date

Carbon Tetrahedral structure Carbon has 4 valence electrons but can bond to fewer than 4 atoms and form double and triple bonds

Hydrocarbons The simplest organic compounds are called hydrocarbons hydrogen carbon In an unsaturated hydrocarbon, the double or triple bond can be broken and carbon can bond to one more atom.

Alkanes Saturated hydrocarbons (all single bonds) are called alkanes Formula for butane: Butane C H ? ?

Alkanes Saturated hydrocarbons (all single bonds) are called alkanes Formula for butane: Butane C H 4 10

Alkanes Saturated hydrocarbons (all single bonds) are called alkanes Formula for butane: Butane C H 4 10 Formula for alkanes: C H n ?

Alkanes Saturated hydrocarbons (all single bonds) are called alkanes Formula for butane: Butane C H 4 10 Formula for alkanes: C H n (2n+2)

Alkanes Saturated hydrocarbons (all single bonds) are called alkanes Formula for butane: C H 4 10 Formula for alkanes: C H n (2n+2)

Alkanes Saturated hydrocarbons (all single bonds) are called alkanes

Alkanes Saturated hydrocarbons (all single bonds) are called alkanes Butane When you observe the structure of butane, you see that a “straight” chain is really not straight nor linear

Naming alkanes To name alkanes: Count the number of carbons Find the corresponding Greek root Add “-ane” to indicate it is an alkane

Naming alkanes Organic chemists call this n-pentane, where n indicates the longest straight chain Longest chain

Naming alkanes To name branched alkanes: 1) Find the parent compound (the longest continuous chain) and add “-ane” to the Greek root

Naming alkanes To name branched alkanes: heptane 1) Find the parent compound (the longest continuous chain) and add “-ane” to the Greek root heptane

Naming alkanes To name branched alkanes: heptane ethyl Find the branch(es) not included and add “-yl” to the Greek root heptane ethyl

Naming alkanes To name branched alkanes: heptane ethyl 3) Find the position at which the branch(es) is (are) located on the parent compound Start counting from the shortest end of the parent compound (here, it is position “4” from both ends) heptane ethyl 1 2 3 4

Naming alkanes 4-ethyl-heptane heptane ethyl This branched alkane is called: 4-ethyl-heptane heptane 1 2 3 4 ethyl

Naming alkanes Here, R = CH2CH3 heptane ethyl The branching group is called the R group Here, R = CH2CH3 heptane ethyl 1 2 3 4

n-butane (C5H12) and isobutane (C5H12) are structural isomers structural isomer: molecule with the same number and type of atoms as another molecule but has a different bonding pattern.

Naming alkanes same molecule isobutane 2-methyl-propane methyl group at position “2” same molecule isobutane 2-methyl-propane methyl group at the second-to-last position 4 carbons in total

Structural isomers Draw and name the structural isomers of pentane (C5H12).

Structural isomers Draw and name the structural isomers of pentane (C5H12). Make a chain of 5 carbons and add hydrogens. n-pentane

Structural isomers Draw and name the structural isomers of pentane (C5H12). Remove a carbon and form a branch in one position. 2-methyl-butane n-pentane

Structural isomers Draw and name the structural isomers of pentane (C5H12). We can remove 2 carbons and form 2 branches in one position. isopentane n-pentane

(2,2,4-trimethyl-pentane) Petroleum chemistry octane isooctane (2,2,4-trimethyl-pentane) Refinement of petroleum generates branched hydrocarbons such as isooctane. Isooctane is better for the car engine because it burns more slowly and more completely than octane.

(2,2,4-trimethyl-pentane) Petroleum chemistry octane isooctane (2,2,4-trimethyl-pentane) 87% isooctane, 13% octane Isooctane is a branched hydrocarbon and has a high octane rating.

(2,2,4-trimethyl-pentane) Petroleum chemistry octane isooctane (2,2,4-trimethyl-pentane) High-performance cars require high-octane fuel Isooctane is a branched hydrocarbon and has a high octane rating.

Types of intermolecular attractions Intermolecular attractions From Chapter 8.3 strong London dispersion Dipole-dipole Hydrogen bonding Types of intermolecular attractions Between polar molecules nonpolar molecules Intermolecular attractions weak Intermolecular attractions are also called van der Waals attractions

Types of intermolecular attractions Intermolecular attractions From Chapter 8.3 strong London dispersion Dipole-dipole Hydrogen bonding Types of intermolecular attractions Between polar molecules nonpolar molecules Intermolecular attractions weak Hydrocarbons Intermolecular attractions are also called van der Waals attractions

Properties of hydrocarbons Between nonpolar molecules With weak intermolecular attraction forces, small hydrocarbons are gases at room temperature. London dispersion

Properties of hydrocarbons As hydrocarbon chains become longer, attraction forces become stronger. Longer hydrocarbons are liquids at room temperature.

n Unsaturated hydrocarbons Polyethylene Ethene or ethylene is a gas at room temperature. It can be used to create the polymer polyethylene in plastics

Unsaturated hydrocarbons Ethyne or acetylene is a hydrocarbon that contains a triple bond. There is more energy in a triple bond than in a double or single bond. Acetylene torches reach temperatures up to 3,300oC (6,000oF) Acetylene torch

Naming unsaturated hydrocarbons To name unsaturated hydrocarbons: Count the number of carbons Find the corresponding Greek root Add “-ene” to indicate a double bond Add “-yne” to indicate a triple bond

Naming unsaturated hydrocarbons To name unsaturated hydrocarbons: Count the number of carbons Find the corresponding Greek root Add “-ene” to indicate a double bond Add “-yne” to indicate a triple bond

Isomers Structural isomers Same formula Different bonding order n-pentane C5H12 2-methyl-butane C5H12 Isopentane C5H12

Isomers Structural isomers Same formula Different bonding order Stereoisomers Same bonding order Different spatial arrangement

Isomers Structural isomers Same formula Different bonding order Stereoisomers Same bonding order Different spatial arrangement Geometric isomers Butene cis configuration (R groups on same side of the C=C bond) double bond

Isomers Structural isomers Same formula Different bonding order Stereoisomers Same bonding order Different spatial arrangement Geometric isomers trans configuration (R groups opposite sides of the C=C bond) Butene cis

Isomers Structural isomers Same formula Different bonding order Stereoisomers Same bonding order Different spatial arrangement Geometric isomers Optical isomers The central carbon is attached to four different groups. Optical isomers are two different molecules!

Aromatic hydrocarbons Cinnamon, cloves, wintergreen and vanilla beans have pleasant, distinctive smells What else do they have in common?

Aromatic hydrocarbons contain one or more benzene rings What else do they have in common? Benzene ring Aromatic hydrocarbons contain one or more benzene rings

Aromatic hydrocarbons Resonance structures of benzene Electrons are always moving, so the single and double bonds on the benzene ring are never fixed. To show that electrons are “delocalized” and equally shared, a circle is used instead.

Naming of hydrocarbons Alkanes Greek root + “-ane” Alkenes Greek root + “-ene” Alkynes Greek root + “-yne” R groups Greek root + “-yl” Saturated hydrocarbons Unsaturated hydrocarbons Hydrocarbon constituents Naming of hydrocarbons Parent compound

Structural isomers Same formula Different bonding order Stereoisomers Same bonding order Different spatial arrangement Geometric isomers Optical isomers cis trans