Ch 22: Organic Chemistry

Section 1: Organic Compounds

• Organic Compounds: covalently bonded compounds containing carbon, excluding carbonates and oxides.

• Carbon is unique in that its electronic structure allows it:

1. to bind to itself to form chains and rings2. to bind covalently to other elements3. to bind to itself and other elements in different

arrangements.

• Catenation: the covalent bonding of an element to itself to form chains or rings. – Can be linked by single, double, or triple covalent

bonds. • Hydrocarbons: composed of only carbon and

hydrogen; they are the simplest organic compounds. – Other organic compounds have hydrocarbon backbones

with elements like O, N, S, and the halogens attached. • Isomers: compounds that have the same

molecular formula but different structures.

Structural Formulas

• Structural Formula: indicates the number and types of atoms present in a molecule and shows the bonding arrangement of the atoms.– A condensed structural formula is when the bond

between Carbon and Hydrogen is not shown.

• Butane can also be CH3—CH2—CH2—CH3

Geometric Isomers• Isomers in which the order of atom bonding is

the same but the arrangement of atoms in space is different.

• Cis: on the same side.• Trans: on opposite sides.

Structural Isomers• Also called “constitutional isomers”, are isomers

in which the atoms are bonded together in different orders. – Ex: Both are C4H10

• Structural Isomers can have different physical or chemical properties. – Ex: Different melting points, boiling points, and density.

Section 2: Hydrocarbons

• Remember, these contain only Carbon and Hydrogen.

• Hydrocarbons are grouped by the type of bonding between the carbon atoms.

• Saturated Hydrocarbons are when each carbon atom in the molecule forms four single covalent bonds with other atoms.

Alkanes• Alkanes: hydrocarbons with only single bonds. • Formula for finding molecular formula for

alkanes: CnH2n+2

• Examples: Find the molecular formula for the following n values.

– n=5– n=12– n=30

– C5H12

– C12H26

– C30H62

Alkanes Cont…

• Only Alkanes with four or more carbon atoms have structural isomers because they can be straight or branched.

• The number of structural isomers increases greatly as the number of carbon atoms in alkanes increases.

Systematic Naming of AlkanesUnbranched-Chain Alkane Nomenclature• Find the prefix that corresponds to the number

of carbon atoms in the chain of the hydrocarbon. • Then add the suffix –ane to the prefix.

CH3—CH2—CH2—CH2—CH2—CH2—CH3

1 2 3 4 5 6 7

7 Carbons is hept- and add –ane to make heptane.

# of Carbon Atoms

Prefix # of Carbon Atoms

Prefix

1 Meth- 6 Hex-2 Eth- 7 Hept-3 Prop- 8 Oct-4 But- 9 Non-5 Pent- 10 Dec-

Branched-Chain Alkane Nomenclature• Alkyl Groups are groups of atoms that are

formed when one hydrogen atom is removed from an alkane molecule.

• Alkyl groups are named by replacing the suffix –ane with –yl.

Alkyl Group Name

-CH3 Methyl

-CH2—CH3 Ethyl

-CH2—CH2—CH3 Propyl

-CH2—CH2—CH2—CH3 Butyl

-CH2—CH2—CH2—CH2—CH3 Pentyl

Alkane Nomenclature1. Name the parent hydrocarbon: find the

longest continuous chain of carbons that have straight-chain branches.

“Prefix for number of carbons” + “-ane”2. Add the names of the alkyl groups: add

them in alphabetical order and if there is more than one of the same group present, attach the appropriate numerical prefix to the name.

3. Number the carbon atoms in the parent hydrocarbon: Number them carbon atoms in the chain to give the lowest numbers possible in the name. If there are two equal lowest positions with two different alkyl groups, give the lowest number to the alkyl group that comes first alphabetically, before prefixes are added.

4. Insert Position Numbers: put position numbers of each alkyl group in front of the name of that group. We do not use the number 1.

5. Punctuate the name: Use hyphens to separate the position numbers from the names. If there is more than one number if front of a name, use commas to separate the numbers.

Examples:Name the following simple branched-chain alkanes:1. CH3—CH—CH2—CH—CH—CH3

| | | CH3 CH3 CH3

2. CH3—CH—CH2—CH3

| CH3

Drawing Alkanes

1. Draw the hydrocarbon chain: Looking at the prefix, determine how many carbons in the parent chain. Leave room to add in hydrogens.

2. Add Alkyl Groups: Using the numbers in the name, determine the locations of any alkyl groups.

3. Correct Alkyl Groups: Using the prefixes, make sure the alkyl groups are correct using the alkyl name. ex. Methyl is CH3 , Ethyl is CH2—CH3

Examples

Draw the condensed structural formula for each of the following:1. 2,4-dimethylpentane2. 4-ethyl-3-methylheptane3. methylpropane

Cycloalkanes

• Cycloalkanes are alkanes in which the carbon atoms are arranged in a ring, or cyclic structure.

• Structural Formula for Cyclopentane.

• Formula for finding molecular formula for cycloalkanes: CnH2n

Homework

• Ch 22.1 pg 714 #1-3and

• Ch 22.2 pg 741 #15-17

Unsaturated Hydrocarbons

• Unsaturated Hydrocarbons: are hydrocarbons in which not all carbon atoms have four single covalent bonds.

• They have one or more double bonds or triple bonds.

• Carbon atoms easily form double and triple bonds to other carbons atoms, so multiple bonds between carbon atoms are common in organic compounds.

Alkenes• Alkenes: hydrocarbons that contain double

covalent bonds• Formula for finding molecular formula for

noncyclic alkenes with one double bond: CnH2n

• Because alkenes have a double bond, they can have geometric isomers.

Systematic Naming of Alkenes• Rules are similar to those for naming an alkane. • The parent hydrocarbon is the longest

continuous chain of carbon atoms that contains the double bond.

• The carbon atoms are numbered so that the first carbon atom in the double bond has the lowest number.

• If there is more than one double bond, the suffix is changed to indicate the number of double bonds. Ex: 2 = -adiene 3 = atriene

Alkene Nomenclature1. Name the parent hydrocarbon: find the

longest continuous chain of carbons that contains the double bond(s).

“Prefix for number of carbons” + “-ene”If more than one double bond, modify the suffix.2. Add the names of the alkyl groups: add

them in alphabetical order and if there is more than one of the same group present, attach the appropriate numerical prefix to the name.

3. Number the carbon atoms in the parent hydrocarbon: Number them carbon atoms in the chain so that the first carbon atom in the double bond nearest the end of the chain has the lowest number. If numbering from both ends gives the same numbers, then number from the end nearest the first alkyl group.

4. Insert Position Numbers: place double-bond position numbers before the name of the parent hydrocarbon and the alkyl group position numbers before the name of the corresponding alkyl group.

5. Punctuate the name: Use hyphens to separate the position numbers from the names. If there is more than one number if front of a name, use commas to separate the numbers.

Examples:Name the following alkenes:

CH3

|1. CH3—CH—C=CH2

| CH2—CH3

2. CH3—CH2—CH2—CH=CH—CH3

Alkynes• Alkynes: hydrocarbons that contain triple

covalent bonds• Formula for finding molecular formula for

noncyclic alkanes with one triple bond: CnH2n-2

Systematic Naming of Alkynes• Rules are similar to those for naming an alkene. • If there is more than one triple bond, the suffix is

changed to indicate the number of triple bonds. Ex: 2 = -adiyne 3 = atriyne

Alkyne Nomenclature1. Name the parent hydrocarbon: find the

longest continuous chain of carbons that contains the triple bond(s).

“Prefix for number of carbons” + “-yne”If more than one triple bond, modify the suffix.

2. Add the names of the alkyl groups: add them in alphabetical order and if there is more than one of the same group present, attach the appropriate numerical prefix to the name.

3. Number the carbon atoms in the parent hydrocarbon: Number them carbon atoms in the chain so that the first carbon atom in the triple bond nearest the end of the chain has the lowest number. If numbering from both ends gives the same numbers, then number from the end nearest the first alkyl group.

4. Insert Position Numbers: place triple-bond position numbers before the name of the parent hydrocarbon and the alkyl group position numbers before the name of the corresponding alkyl group.

5. Punctuate the name: Use hyphens to separate the position numbers from the names. If there is more than one number if front of a name, use commas to separate the numbers.

Examples:Name the following alkynes:1. CH≡C—CH—CH3

| CH3

2. CH3—CH2—CH2—C≡CH

Aromatic Hydrocarbons• Aromatic Hydrocarbons: have six-membered

carbon rings and delocalized electrons. • Benzene: is the primary aromatic hydrocarbon.

C6H6 It is a six carbon atom ring with three double bonds.

Section 3: Functional Groups

• Functional Group: is an atom or group of atoms that is responsible for the specific properties of an organic compound.

• Compounds that contain the same functional group can be classified together because they will undergo the same types of chemical reactions.

Classes of Organic Compounds• Alcohols: are organic compounds that contain

one or more hydroxyl groups.– Functional Group: —OH

• Alkyl Halides: are organic compounds in which one or more halogen atoms—fluorine, chlorine, bromine, or iodine—are substituted for one or more hydrogen atoms.– Functional Group: —X (X= F, Cl, Br, or I)

• Ether: are organic compounds in which two hydrocarbon groups are bonded to the same atom of oxygen. – Functional Group: —O—

• Aldehydes: are organic compounds in which the carbonyl group is attached to a carbon atom at the end of a carbon-atom chain.

O||

– Functional Group: —C—H

• Ketone: are organic compounds in which the carbonyl group is attached to carbon atoms within the chain.

O||

– Functional Group: —C— • Amine: are organic compounds that can be

considered to be derivatives of ammonia, NH3.– Functional Group: —N—

|

• Carboxylic Acids: are organic compounds that contain the carboxyl functional group.

O||

– Functional Group: —C—OH • Ester: are organic compounds that have

carboxylic acid groups in which the hydrogen of the hydroxyl group has been replaced by an alkyl group.

O||

– Functional Group: —C—O—

Homework

• Ch 22.2 pg 729 #5 and pg 742 #19-20and

• Ch 22.3 pg 734 #1