Introduction to Organic Chemistry Organic chemistry is the study of compounds that contain the element carbon. Organic chemicals affect virtually every facet of our lives. Products such as clothes, foods, medicines, gasoline, refrigerants, and soaps are composed almost solely of organic compounds. Because organic compounds are composed of covalent bonds, their properties differ a great deal from those of ionic inorganic compounds.

Characteristic Features of Organic Compounds All organic compounds contain carbon atoms and most contain hydrogen atoms. Carbon has four valence electrons available for bonding. Hydrogen has a single valence electron and can only form single bonds.

Characteristic Features of Organic Compounds Carbon forms single, double, and triple bonds to other carbon atoms.

Characteristic Features of Organic Compounds Some compounds have chains of atoms and some compounds have rings.

Characteristic Features of Organic Compounds 4. Organic compounds may also contain elements other than carbon and hydrogen. Any atom that is not carbon or hydrogen is called a heteroatom. Each heteroatom forms a characteristic number of bonds, determined by its location in the periodic table. The common heteroatoms (N, O, F, Cl, Br, and I) also have nonbonding, lone pairs of e−, so that each atom is surrounded by eight electrons. # of bonds + # of lone pairs = 4

Characteristic Features of Organic Compounds 4. Organic compounds may also contain elements other than carbon and hydrogen, (heteroatoms ) Each heteroatom forms a characteristic number of bonds, determined by its location in the periodic table.

Characteristic Features of Organic Compounds The most common multiple bond between carbon and a heteroatom is a carbon–oxygen double bond.

Drawing Organic Molecules Condensed Structures In a condensed structure, all of the atoms are drawn in, but the two-electron bond lines and lone pairs on heteroatoms are generally omitted. A carbon bonded to 3 Hs becomes CH3. A carbon bonded to 2 Hs becomes CH2.

Drawing Organic Molecules Condensed Structures Sometimes structures are further simplified by using parentheses around like groups. Two CH2 groups bonded together become (CH2)2. Two CH3 groups bonded to the same carbon become (CH3)2C.

Drawing Organic Molecules Skeletal Structures When drawing a skeletal structure: Assume there is a carbon atom at the junction of any two lines or at the end of any line. Assume there are enough hydrogens around each carbon to give it four bonds. Draw in all heteroatoms and the hydrogens directly bonded to them.

Drawing Organic Molecules Skeletal Structures

Functional Groups A functional group is an atom or group of atoms with characteristic chemical and physical properties. A functional group contains a heteroatom, a multiple bond, or sometimes both. The letter R is used to abbreviate the carbon and hydrogen portion of a molecule.

Functional Groups Hydrocarbons Hydrocarbons are compounds that contain only carbon and hydrogen. Alkanes have only C–C single bonds and no functional group. Alkenes have a C–C double bond as their functional group. Alkynes have a C–C triple bond as their functional group. Aromatic hydrocarbons contain a benzene ring, a six-membered ring with three double bonds.

Functional Groups Compounds Containing a C=O group Carbonyl groups (carbon–oxygen double bonds) are present in several different compounds.

Functional groups .

Alkanes Introduction Alkanes are hydrocarbons having only C–C and C–H single bonds. Alkanes that contain chains of C atoms but no rings are acyclic alkanes and have the general formula CnH2n+2. Acyclic alkanes are called saturated alkanes because they have the maximum number of H atoms per C atom. 16 16

Alkanes Introduction Cycloalkanes contain C atoms joined in one or more rings. They have the general formula CnH2n. All alkane molecules have names that end in the suffix “-ane.” 17 17

Simple Alkanes Acyclic Alkanes Having Fewer than Five Carbons Methane is a one-carbon alkane. 18 18

Simple Alkanes Acyclic Alkanes Having Fewer than Five Carbons Ethane is a two-carbon alkane. 19 19

Simple Alkanes Acyclic Alkanes Having Fewer than Five Carbons Propane is a three-carbon alkane. 20 20

Simple Alkanes Acyclic Alkanes Having Fewer than Five Carbons The following two representations of propane are equivalent: The bends in a carbon chain don’t matter when it comes to identifying different compounds. 21 21

Simple Alkanes Acyclic Alkanes Having Fewer than Five Carbons Butane has four-carbon atoms in a row. It is a straight-chain alkane. Isobutane has three carbon atoms in a row and one bonded to the middle. It is a branched-chain alkane. 22 22

Simple Alkanes Acyclic Alkanes Having Fewer than Five Carbons Butane and isobutane are isomers of each other. Isomers are two different compounds with the same molecular formula. Constitutional isomers differ in the way the atoms are connected to each other. Another example of constitutional isomers: 23 23

Simple Alkanes Acyclic Alkanes Having Five or More Carbons As the number of C atoms increases, the number of possible isomers increases. Pentane is a five-carbon alkane with three isomers: 24 24

Simple Alkanes Acyclic Alkanes Having Five or More Carbons After pentane, the following names apply: # of C’s Name Structure 6 hexane CH3CH2CH2CH2CH2CH3 7 heptane CH3CH2CH2CH2CH2CH2CH3 8 octane CH3CH2CH2CH2CH2CH2CH2CH3 9 nonane CH3CH2CH2CH2CH2CH2CH2CH2CH3 10 decane CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3 25 25

An Introduction to Nomenclature The IUPAC System of Nomenclature IUPAC stands for International Union of Pure and Applied Chemistry. The IUPAC system of nomenclature provides a system of naming organic compounds. Using the IUPAC system, each organic compound gets an unambiguous name. 26 26

Alkane Nomenclature Naming Substituents Carbon substituents are called alkyl groups. An alkyl group is formed by removing 1 H from an alkane. To name an alkyl group, change the “-ane” ending of the parent alkane to “-yl.” Each alkyl group has a bond that can then be attached to something else. 27 27

Alkane Nomenclature Naming Substituents 28 28

Alkane Nomenclature Naming Substituents 29 29

Alkane Nomenclature Naming an Acyclic Alkane HOW TO Name an Alkane Using the IUPAC System The longest chain may not be written horizontally. It does not matter if the chain is straight or has bends. All three examples below have 6 Cs in their longest chain: 30 30

Alkane Nomenclature Naming an Acyclic Alkane HOW TO Name an Alkane Using the IUPAC System Find the parent carbon chain and add the suffix. Step [1] Find the longest continuous carbon chain, and name it with an “-ane” ending. 31 31

Alkane Nomenclature Naming an Acyclic Alkane HOW TO Name an Alkane Using the IUPAC System Number the atoms in the carbon chain to give the first substituent the lower number. Step [2] CORRECT INCORRECT 32 32

Alkane Nomenclature Naming an Acyclic Alkane HOW TO Name an Alkane Using the IUPAC System The following compound contains two methyl groups, so we use the name dimethyl for them. 33 33

Alkane Nomenclature Naming an Acyclic Alkane Sample Problem 10.9 Give the IUPAC name for the following compound. ethyl at C5 methyl at C2 CH3 CH3 CH3CH2 CH3CH2 H CH3 C CH2CH2 C C CH2CH3 H H CH3 CH3 methyl at C6 1 2 5 6 longest chain is 8 Cs = octane 5-ethyl-2,6-dimethyloctane Answer 34 34

Cycloalkanes Naming Cycloalkanes 35 35

Cycloalkanes Naming Cycloalkanes HOW TO Name a Cycloalkane Using the IUPAC System Step [1] Find the parent cycloalkane. 36 36

Cycloalkanes Naming Cycloalkanes HOW TO Name a Cycloalkane Using the IUPAC System Step [2] Name and number the substituents. No number is needed for a cycloalkane with a single substituent. 37 37

Cycloalkanes Naming Cycloalkanes HOW TO Name a Cycloalkane Using the IUPAC System For rings with two or more substituents: begin numbering at one substituent then, proceed around the ring to give the second substituent the lower number For two different substituents, number the ring to assign the lower number to the substituents alphabetically. 38 38

Cycloalkanes Naming Cycloalkanes HOW TO Name a Cycloalkane Using the IUPAC System Earlier letter = lower number ethyl group at C1 methyl group at C3 1-ethyl-3-methylcyclohexane (not 3-ethyl-1-methylcyclohexane) 39 39

Physical Properties Alkanes contain only nonpolar C–C and C–H bonds. Alkanes exhibit only weak intermolecular forces, so they have low melting points and boiling points. Smaller alkanes are gases at room temperature, whereas larger alkanes are liquids. Alkanes are insoluble in water. Alkanes are less dense than water, meaning that they will float on the surface of water. 40 40

Physical Properties As the number of carbons in an alkane increases, the boiling point increases: 41 41

Combustion Alkanes have no functional group, so they undergo few reactions. Combustion is the only reaction of alkanes in this chapter. It is an oxidation reaction. In the combustion reaction, alkanes burn in the presence of O2 gas to form CO2 and H2O. 42 42

Combustion The products, CO2 + H2O, are the same, regardless of the identity of the alkane that undergoes combustion. Combustion of alkanes in the form of natural gas, gasoline, or heating oil releases energy for heating homes, powering vehicles, and cooking food. 43 43

Combustion If there is not enough O2 to react, incomplete combustion may occur, and carbon monoxide (CO) is formed instead of carbon dioxide (CO2). Carbon monoxide is a poisonous gas that binds to hemoglobin in blood, thereby reducing the amount of O2 that can be transported to cells. 44 44