Organic Chemistry

Introduction

Organic Chemistry

- is the study of compounds that contain carbon.

There are lots of them.90% + of known compounds are OrganicWhy?Because carbon forms chains

Hydrocarbons

Organic compounds that contain only hydrogen and carbon.

Alkanes

Hydrocarbons containing only single covalent bonds

Ex: CH4 – methane – natural gas

Dot diagram

Dashes

Reminders about dot diagrams

Only show 2 D shapeCarbon likes to bond in ____ placesHydrogen likes to bond in ____ place

Dot diagram for C2H6

Straight-chain alkanes

Contain any number of C atoms, one after the other, in a chain.

You should know the names of these next alkanes

First 10 straight-chained alkanes

Methane CH4 CH4

Ethane C2H6 CH3CH3

Propane C3H8 CH3CH2CH3

Butane C4H10 CH3CH2CH2CH3

Pentane C5H12 CH3CH2CH2CH2CH3

Hexane C6H14 CH3CH2CH2CH2CH2CH3

Heptane C7H16 CH3CH2CH2CH2CH2CH2CH3

Octane C8H18 CH3CH2CH2CH2CH2CH2CH2CH3

Nonane C9H20 CH3CH2CH2CH2CH2CH2CH2CH2CH3

Decane C10H22 CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3

Homologous series

A group of compounds in which there is a constant increment of change in molecular structure from one compound in the series to the next.

The alkanes differ by one CH2 group each time

CnH2n+2

Types of formulas

Molecular formula – C4H10

Complete structural formula

Condensed structural formula – C – H bonds are understood.

Condensed structural formula – C-H and C-C bonds understood

Carbon skeleton; hydrogens understood

Draw a complete structural formula for the straight-chained alkane having 3 carbons

Branched-chain Alkanes

Substituent – an atom or group of atoms that can take the place of a hydrogen atom on a parent hydrocarbon molecule.

Parent chain – the longest carbon chain.May not always be written in a straight line on

paper.

Alkyl group – a hydrocarbon substituent

CH3 – methyl

CH3CH2 – ethyl

CH3CH2CH2 – propyl

Alkyl group = alkane – 1 HName = -ane + ylWhat would CH3CH2CH2 CH2be called?

Branched-chain alkane

An alkane with one or more alkyl groups attached.

Naming a branched-chain alkane

1. Find the longest chain of carbons. This is the parent chain

2. # the carbons on the parent chain. Starting with the end that will give the substituents the smallest numbers

3. Add #s to the names of the substituent groups to identify their positions on the chain.

4. Use prefixes to indicate if a group appears more than once. Di – 2Tri – 3Tetra – 4Penta – 5

5. List the names of the alkyl substituents in alphabetical order (ignore prefixes when alphabetizing.)

6. Use proper punctuationCommas separate #s from #sHyphens separate #s from words

Properties of alkanes

Nonpolar – electrons are shared about equally

Very weak van der Walls forces (dispersion)

Have a low mass, low boiling pointDo not dissolve in water.Flammable