Organic Chemistry  Introduction to Organic Chemistry  Alkanes

What is Organic Chemistry? What do you think of when you hear the word organic?Inorganic? What do you think of when you hear the word organic?Inorganic? Inorganic Chemistry is the study of the rest of the elements Inorganic Chemistry is the study of the rest of the elements Organic Chemistry is the study of carbon containing compounds Organic Chemistry is the study of carbon containing compounds

What is Organic Chemistry? Historically, organic compounds were obtained naturally from plants and animals Historically, organic compounds were obtained naturally from plants and animals We now have found ways of synthesizing these organic compounds (with the desirable properties of the natural compounds) We now have found ways of synthesizing these organic compounds (with the desirable properties of the natural compounds)

Why is Carbon so Special? The unique characteristics of carbon allow for large number of organic compounds The unique characteristics of carbon allow for large number of organic compounds Carbon forms a total of four covalent bonds Carbon forms a total of four covalent bonds Thus it can bond to itself or many different atoms Thus it can bond to itself or many different atoms Forms single, double or triple bonds Forms single, double or triple bonds

Representing Structures There are a number of different ways to draw our compounds There are a number of different ways to draw our compounds

Structural Formula Shows all the atoms in a structure and how they are bonded to one another Shows all the atoms in a structure and how they are bonded to one another Are 2-D drawings of 3-D objects thus they are not totally accurate Are 2-D drawings of 3-D objects thus they are not totally accurate

“—”A single line represents one pair of electrons (a single bond) “=” A double line represents two pairs of electrons (a double bond) “ ≡ ”A triple line represents three pairs of electrons (a triple bond)

Condensed Structural Formula Shows the kind and number of atoms present Shows the kind and number of atoms present Only shows bonds between carbon atoms Only shows bonds between carbon atoms The bond between hydrogen and carbon is assumed to be present The bond between hydrogen and carbon is assumed to be present

Expanded Molecular Formula Shows the kind and number of atom present in the compound Shows the kind and number of atom present in the compound Does not show the actual bonds that occur, however they are assumed to be present Does not show the actual bonds that occur, however they are assumed to be present When written as a molecular formula, the above example becomes C 3 H 8 When written as a molecular formula, the above example becomes C 3 H 8

Skeletal Formula The end of each line, and the points where lines meet, represent carbon atoms The end of each line, and the points where lines meet, represent carbon atoms Hydrogen atoms are assumed to be present in the correct number Hydrogen atoms are assumed to be present in the correct number You may see this in some books and online etc but we will not focus on this! You may see this in some books and online etc but we will not focus on this!

Terms Saturated:organic compounds in which each carbon atom is bonded to the maximum number of hydrogen atoms, thus containing only single bonds Saturated:organic compounds in which each carbon atom is bonded to the maximum number of hydrogen atoms, thus containing only single bonds Unsaturated:organic compounds in which the carbon atoms do not have the maximum number of hydrogen atoms and thus have double or triple bonds Unsaturated:organic compounds in which the carbon atoms do not have the maximum number of hydrogen atoms and thus have double or triple bonds

Terms Hydrocarbons:organic compounds consisting of only carbon and hydrogen Hydrocarbons:organic compounds consisting of only carbon and hydrogen –Straight Chain: all C bonded to only 2 other Ceg. C-C-C-C –Branched Chain: one or more C bonded to 3 or 4 other C’seg. C | C – C – C | C

Classifying Hydrocarbons Look at the following compounds. If you were to classify them, how would you do it?

Single Bond Compounds These are called Alkanes!

Double Bond Compounds These are called Alkenes!

Triple Bond Compounds These are called Alkynes!

Classifying Hydrocarbons These are the three groups of hydrocarbons These are the three groups of hydrocarbons 1.Alkane 2.Alkene 3.Alkyne We will now look at these further We will now look at these further

Alkanes Single Bonds C—C Are saturated hydrocarbons Are saturated hydrocarbons Each molecule differs from the next by the structural unit –CH 2 – Each molecule differs from the next by the structural unit –CH 2 – This is a homologous series – when each member increases by the same structural unit This is a homologous series – when each member increases by the same structural unit The General formula for an alkane is The General formula for an alkane is C n H 2n+2

Properties of Alkanes Non-polar Non-polar Thus are soluble in non-polar solvents and not soluble in polar solvents Remember: Like Dissolves Like Thus are soluble in non-polar solvents and not soluble in polar solvents Remember: Like Dissolves Like Have relatively low boiling points Have relatively low boiling points Boiling points, melting points and densities of straight-chain alkanes increase with increasing chain length Boiling points, melting points and densities of straight-chain alkanes increase with increasing chain length

Naming Straight-Chain Alkanes All alkanes end with the suffix –ane All alkanes end with the suffix –ane Root of the name is based on the number of carbons in the chain Root of the name is based on the number of carbons in the chain Examples:Methane1 Carbon Examples:Methane1 Carbon Ethane2 Carbon What is the molecular formula of each?

Prefix# Carbon Atoms Meth1 Eth2 Prop3 But4 Pent5 Hex6 Hept7 Oct8 Non9 Dec10

What is the name of this compound? What is the name of this compound? CH 3 —CH 2 —CH 2 —CH 2 —CH 3 Draw the structure for this compound. Draw the structure for this compound.Octane

Naming Branched-Chain Alkanes These molecules have side chains (branches) that can be made up of alkyl groups or halogens These molecules have side chains (branches) that can be made up of alkyl groups or halogens We name these based on their parent chain (longest alkane) and side chains We name these based on their parent chain (longest alkane) and side chains Naming follows the general formula: Naming follows the general formula: Prefix + Root + Suffix

Prefix: the branches attached to the parent chain Prefix: the branches attached to the parent chain Root: the longest continuous chain in the hydrocarbon (the parent chain) Root: the longest continuous chain in the hydrocarbon (the parent chain) Suffix: for all alkanes, the suffix is –ane Suffix: for all alkanes, the suffix is –ane

Alkyl Branches Alkyl groups are alkanes with one less hydrogen Alkyl groups are alkanes with one less hydrogen They are named as alkanes are, with the ending –yl They are named as alkanes are, with the ending –yl Eg. Alkane:PropaneCH 3 CH 2 CH 3 Eg. Alkane:PropaneCH 3 CH 2 CH 3 Alkyl Group: PropylCH 3 CH 2 CH 2 Alkyl Group: PropylCH 3 CH 2 CH 2

Halogen Branches Halogen branches are given names based on their element name, with any ending removed Halogen branches are given names based on their element name, with any ending removed Eg. BrBromo Eg. BrBromo ClChloro

Naming the branches Prefixes are numbered based on their position along the parent chain – these numbers are always given such that the branch has the lowest possible number! Prefixes are numbered based on their position along the parent chain – these numbers are always given such that the branch has the lowest possible number! When putting prefixes together in the name: When putting prefixes together in the name: –Numbers are put in ascending order –Hyphens separate numbers and words –Commas separate numbers

How does this go together? CH 3 –CH–CH 2 –CH 3 | CH 3 CH 3

Steps for Naming 1. Find the root – locate the parent alkane 2. Find position numbers – number the parent chain starting with the end closest to the branch 3. Find the prefix – name the branches 4. Put it together! Prefix + Root + Suffix

Try One More Cl Cl | CH 3 –CH—CH—CH 2 CH 3 | CH 2 –CH 3 CH 2 –CH 3