Organic Chemistry

Organic chemistry is the chemistry of the carbon atom. It is the chemistry of all life on earth. Carbon atoms bond to other atoms of carbon hydrogen and sometimes oxygen, nitrogen, sulfur and phosphorus A few compounds contain carbon but are not considered to be organic: CO 2, CO, H 2 CO 3, CaCO 3

Hydrocarbons Hydrocarbons are the simplest organic molecules. They are made of only carbon C and hydrogen H atoms Each carbon atom makes 4 bonds Each hydrogen atom makes 1 bond -H If each carbon makes only one bond to each of its neighbours, it is called an ‘alkane’

Systematic Nomenclature International Union of Pure and Applied Chemistry (IUPAC) Committee on Organic Nomenclature # C 1meth-6hex- 2eth-7hept- 3prop-8oct- 4but-9non- 5pent-10dec-

Methane (CH 4 ) CH 4 Ethane (C 2 H 6 )CH 3 CH 3 Propane (C 3 H 8 )CH 3 CH 2 CH 3 bp -160°C bp -89°C bp -42°C The Simplest Alkanes have only C and H, only single bonds, and all names end in ‘ane’

CH 3 CH 2 CH 2 CH 2 CH 2 CH 3 Pentane Hexane CH 3 CH 2 CH 2 CH 2 CH 3 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 Heptane Butane CH 3 CH 2 CH 2 CH 3

The alkanes

Nomenclature of the Alkanes Alkanes always have the ending -ane. Side chains (substituents) are named as alkyl groups.

Common alkyl groups (C 1 through C 4 )

IUPAC nomenclature of alkanes 1. identify the longest chain -- parent 2. number from the end closest to first branch 3. Name the groups attached to the chain, using the carbon number as the locator. 4. Alphabetize substituents. 5. Use di-, tri-, etc., for multiples of same substituent 6. combine number and name of substituent with parent name, separating with hyphen

Longest Chain The number of carbons in the longest chain determines the base name: ethane, hexane. If there are two possible chains with the same number of carbons, use the chain with the most branches (substituents). =>

Number the Carbons Start at the end closest to the first attached group. If two substituents are equidistant, look for the next closest group

Organic nomenclature methylbutane

Naming Branched Alkanes address # - branch name + yl+ parent name 2-methylpropane

Find the longest continuous carbon chain methylpentane

You must choose the longest continuous carbon chain ethylheptane

Number from the end nearest the first substituent ethyl-3-methylheptane

Number from the end nearest the first substituent ethyl-5-methyloctane

Use “di-” with two substituents ,3-dimethylbutane

Every substituent must get a number ,3-dimethylhexane

Number from the end nearest first substituent ,7,8-trimethyldecane

Number from the end which has the “first difference” ,4,8-trimethyldecane

A More-Highly-Substituted Carbon Takes Precedence ,2,4-Trimethylpentane

Which end do we number from? ethyl-6-methyloctane

IUPAC rules 1. Find the longest straight chain = parent chain 2. Number the parent chain in the direction that gives the lowest number to the substituents at the first point of difference. 3. Two or more identical groups are indicated by di, tri, tetra, etc. Longest chain is 7 (not 6). This is 3-methylheptane.. 2,3,6-trimethylheptane (not 2,5,6-trimethyl heptane) 2,2,6,6,7-pentamethyloctane (not 2,3,3,7,7-pentamethyloctane)

4. Different groups are listed in alphabetical order (di, tri, tetra, etc. don’t count). 5. If the numbering is the same in both directions, choose the numbering to follow the alphabetical order. IUPAC rules 6-ethyl-2,2-dimethyloctane 5-ethyl-6-methyldecane

6. When two or more chains compete for the longest, the choice goes to the one with the greater number of side groups. IUPAC rules 2,4,6-trimethyl-5-propyloctane

IUPAC rules 6-ethyl-2,2,5,7-tetramethylnonane (not 6,7-diethyl-2,2,5-trimethyloctane. Name the following compounds.

Good Luck! 7-(1,1-Dimethylbutyl)-3-ethyl-7-methyldodecane

Halogens and other side groups Flouro –F Chloro –Cl Bromo –Br Iodo –I Nitro –NO 2

Bromoethane “Ethyl bromide”

2-Chloro-2-methylpropane

2-Bromo-3-methylpentane

Common Nomenclature Pitfalls Did not find the longest carbon chain Numbered chain from the wrong end Forgot to repeat number for each identical substituent; forgot to use di- tri- tetra-, etc. Writing the name as more than one word Incorrect punctuation

cyclic molecules

Nomenclature for Cyclic Alkanes For compounds with a single ring, add the prefix “cyclo-” to the root name for the alkane comprising the ring.

Nomenclature of the Substituted Cycloalkanes If there is only one substituent, do not use the “1”. If there is more than one substituent, you must use all numbers, including “1”! Number around the ring in a direction to get from the first substituent to the second substituent by the shorter path. For equivalent degrees of substitution, number in a direction that follows the alphabetical sequence. A carbon with greater substitution has precedence in numbering.

Bromocyclopropane

1,1-Dimethylcyclohexane

4-Ethyl-1,1-dimethylcyclohexane

Numbering Starts at the Most Highly-Substituted Carbon Chloro-1,1,6-trimethylcycloheptane

cycloalkyl groups

3-Cyclobutyl-3-methylpentane

2-Cyclobutylbutane

Name the following cycloalkanes. IUPAC rules 1,1,2-trimethycyclohexane