Post on 11-May-2015
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