Introduction to Organic Chemistry

Do Now: Write down the definition of an “organic” compound Write down the definition of an “inorganic” compound

Organic Compound Organic chemistry is the chemistry of carbon compounds. Life on our planet is based on carbon and organic means “to do with living beings.” Nowadays we make our own carbon-based materials. There are over 10 million carbon compounds.

Why is Carbon So Special? Hints: Look at the number of electrons in its outer shell How many bonds can it form? What type of bonds does it form? What type of STRUCTURES/molecules does it form? Use your PT to draw the electronic structure of a carbon atom. What is so special about it? It can form rings and very long chains, which can be branched. This is because: a carbon atom has four electrons in its outer shell, so it forms four covalent bonds Carbon-carbon bonds are relatively strong (346kJmol-1) and non-polar Carbon-hydrogen bond is also strong (413kJmol-1) and hydrocarbon chains form the skeleton of most organic compounds.

A branched hydrocarbon chain A hydrocarbon ring Ask pupils to draw a hydrocarbon chain of an alkane with 6 carbons in a straight chain. Can they name it? Can they give the general formula? Ask pupils to draw a hydrocarbon chain of an alkane with 6 carbons in a “Branched” chain. Mayhave to explain term branched. Make sure that the pupils know that each C should still have 4 covalent bonds. Ask pupils to draw a hydrocarbon chain of an alkane with 6 carbons in a ring.

Bonding in Carbon Compounds In all stable carbon compounds, carbon forms four covalent bonds and has eight electrons in its outer shell. It can do this by forming bonds in different ways. What ways do you think they can bond?

Single Bond: E.g., Methane Extension: Ask pupils to draw SHAPE of methane and give its bond angles.

Double Bond: E.g., Ethene Extension: Ask pupils to draw SHAPE of ethene and give its bond angles.

Triple Bond: Ethyne Extension: Ask pupils to draw SHAPE of ethyne and give its bond angles.

Formulae of Carbon Compounds Empirical Molecular Displayed Structural Skeletal

Empirical Formula On white boards: Write the definition ... GO!! “The simplest whole number ratio of the atoms of each element present in a compound.” E.g., A compound contains 85.7% C and 14.3% H. What is its empirical formula? C H 85.7 14.3 12 1 7.14 14.3 7.14/7.14 =1 14.3/7.14=2 CH2 Pupils should know the definition from Amount of Substance Topic.

Molecular Formula On white boards: Write the definition ... GO!! “The formula that shows the ACTUAL number of atoms of each element in a molecule.” E.g., The Mr of the previous compound is 42. What is the molecular formula of the compound? Empirical formula = CH2 Empirical Mr = 14 42/14 = 3 Molecular formula = C3H6 Check that C3H6 = 42 Pupils should know the definition from Amount of Substance Topic.

Displayed Formula This shows every atom and every bond in the molecule. – Single Bond = Double Bond Ξ Tripe Bond

Displayed Formula Examples C2H4 CH4O

Displayed Formulas Draw the displayed formulas for the following compounds: Methane (CH4) Ethane (C2H6) Ethanol (C2H6O)

Structural Formula This shows the unique arrangement of atoms in a molecule in a simplified form, without showing all the bonds. Each carbon is written separately, with the atoms or groups that are attached to it. Write the structural formula from left to right. Example CH3CH3

Structural Formula How would this compound be written?

Now it’s your turn 1 2 3 4

The Branches Branches in the carbon chains are shown in brackets: CH3CH(CH3)CH3

What do you Think the Structural Formula of These Branched Carbon Chains Are? CH3CH(CH3)CH(CH3)CH3 CH3CH2CH(CH3)CH3 CH3C(CH3)2CH(CH3)CH2CH3

Skeletal Structures These ABBREVIATE displayed formulas by OMITTING H ATOMS and representing C TO C BONDS AS STRAIGHT LINES such that the points where lines meet or the ends of lines represent the C atoms Don't be fooled: The hydrogen atoms are present in the molecules but their presence is assumed - rather than drawn or stated.

Skeletal Structures Draw skeletal structures for: Propane Butane Pentane Hexane Heptane

Skeletal Structures

REPRESENTING MOLECULAR STRUCTURES: Summary Three different formats may be used: 1. DISPLAYED FORMULAS these show ALL atoms and ALL bonds 2. STRUCTURAL FORMULAS these ABBREVIATE displayed formulas to a single line representation 3. SKELETAL FORMULAS these ABBREVIATE displayed formulas by OMITTING H ATOMS and representing C TO C BONDS AS STRAIGHT LINES such that the points where lines meet or the ends of lines represent the C atoms H C O 1. OH 3. CH3C(CH3)(OH)CH3 2. All represent 2-methylpropan-2-ol

Summary Questions A compound comprising only carbon and hydrogen, in which 4.8g of carbon combine with 1.0g of hydrogen, has relative molecular mass of 58. How many moles of carbon are there in 4.8g? How many moles of hydrogen are there in 1.0g? What is the empirical formula of this compound? What is the molecular formula of this compound? Draw the structural formula of the compound that has a straight chain. Draw the displayed formula of the compound that has a branched chain.

Summary Questions A compound comprising only carbon and hydrogen, in which 4.8g of carbon combine with 1.0g of hydrogen, has relative molecular mass of 58. How many moles of carbon are there in 4.8g? 0.4 mol How many moles of hydrogen are there in 1.0g? 1.0 mol What is the empirical formula of this compound? C2H5 What is the molecular formula of this compound? C4H10 Draw the structural formula of the compound that has a straight chain. Draw the displayed formula of the compound that has a branched chain.

Finisher Starter for 10 5.1.2 Nomenclature RSC Starter for 10 5.1.3 Formulae