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: to bind to itself to form chains and rings to bind covalently to other elements 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

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.

Systematic Naming of Alkanes Unbranched-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 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

“Prefix for number of carbons” + “-ane” Alkane Nomenclature Name the parent hydrocarbon: find the longest continuous chain of carbons that have straight-chain branches. “Prefix for number of carbons” + “-ane” 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.

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. 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. 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: CH3—CH—CH2—CH—CH—CH3 | | | CH3 CH3 CH3 CH3—CH—CH2—CH3 | CH3

Drawing Alkanes Draw the hydrocarbon chain: Looking at the prefix, determine how many carbons in the parent chain. Leave room to add in hydrogens. Add Alkyl Groups: Using the numbers in the name, determine the locations of any alkyl groups. 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: 2,4-dimethylpentane 4-ethyl-3-methylheptane methylpropane

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 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 Nomenclature 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. 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.

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. 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. 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 | CH3—CH—C=CH2 CH2—CH3 CH3—CH2—CH2—CH=CH—CH3

Alkynes Alkynes: hydrocarbons that contain triple covalent bonds

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 Nomenclature 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. 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.

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. 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. 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: CH≡C—CH—CH3 | CH3 CH3—CH2—CH2—C≡CH