* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Introduction and Alk.. - hrsbstaff.ednet.ns.ca
Survey
Document related concepts
Transcript
Organic Chemistry Introduction Alkanes to Organic Chemistry What is Organic Chemistry? What do you think of when you hear the word organic? Inorganic? Organic Chemistry is the study of carbon containing compounds Inorganic Chemistry is the study of the rest of the elements What is Organic Chemistry? 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) Why is Carbon so Special? The unique characteristics of carbon allow for large number of organic compounds Carbon forms a total of four covalent bonds Thus it can bond to itself or many different atoms Forms single, double or triple bonds Representing Structures 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 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 Only shows bonds between carbon atoms 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 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 C3H8 Skeletal Formula 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 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 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 – Straight Chain: all C bonded to only 2 other C eg. C-C-C-C – Branched Chain: one or more C bonded to 3 or 4 other C’s eg. 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 1. Alkane 2. Alkene 3. Alkyne We will now look at these further Alkanes Single Bonds C—C Are saturated hydrocarbons Each molecule differs from the next by the structural unit –CH2– This is a homologous series – when each member increases by the same structural unit The General formula for an alkane is CnH2n+2 Properties of Alkanes Non-polar Thus are soluble in non-polar solvents and not soluble in polar solvents Remember: Like Dissolves Like Have relatively low boiling points 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 Root of the name is based on the number of carbons in the chain Examples: Methane Ethane 1 Carbon 2 Carbon What is the molecular formula of each? Prefix # Carbon Atoms Meth 1 Eth 2 Prop 3 But 4 Pent 5 Hex 6 Hept 7 Oct 8 Non 9 Dec 10 What is the name of this compound? CH3—CH2—CH2—CH2—CH3 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 We name these based on their parent chain (longest alkane) and side chains Naming follows the general formula: Prefix + Root + Suffix Prefix: the branches attached to the parent chain Root: the longest continuous chain in the hydrocarbon (the parent chain) Suffix: for all alkanes, the suffix is –ane Alkyl Branches Alkyl groups are alkanes with one less hydrogen They are named as alkanes are, with the ending –yl Eg. Alkane: Alkyl Group: Propane CH3CH2CH3 Propyl CH3CH2CH2 Halogen Branches Halogen branches are given names based on their element name, with any ending removed Eg. Br Cl Bromo Chloro 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! 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? CH3–CH–CH2–CH3 | CH3 Steps for Naming 1. 2. 3. 4. Find the root – locate the parent alkane Find position numbers – number the parent chain starting with the end closest to the branch Find the prefix – name the branches Put it together! Prefix + Root + Suffix Try One More Cl | CH3–CH—CH—CH2CH3 | CH2–CH3 Recap of Naming 1. Find the root – locate the parent alkane (the longest carbon chain – it is not always a straight line!) 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 When putting a name together… Commas separate numbers from numbers Hyphens separate numbers from letters Numbers are put in ascending order ie. 1,2,3 When putting a name together… Branch names are placed in alphabetical order Except!!!! When using di and tri for multiple branches, we order by the branch name and not the prefix eg. dimethyl - order by the “m” not the “d”