Hydrocarbons Intro Lesson PDF

ORGANIC CHEMISTRY -Organic molecules contain only C, H, O, N and sometimes S and P -56 204 570 organic substances have been recorded What allows for the diversity of organic compounds? -Carbon can make 4 bonds -The 4 bonds can be a combination of single, double, and triple bonds methan...

ORGANIC CHEMISTRY -Organic molecules contain only C, H, O, N and sometimes S and P -56 204 570 organic substances have been recorded What allows for the diversity of organic compounds? -Carbon can make 4 bonds -The 4 bonds can be a combination of single, double, and triple bonds methane, CH4 methanal, CH2O ethanenitrile, CH3CN Naming Hydrocarbons  What’s in a Name Assembled from components that describe various features of the molecule. root suffix Functional Number of group carbons in the longest chain Ex: methane Ex: butanol  Root Name = Longest Chain The longest continuous chain of carbons containing the principal functional group defines the root name. Other groups attached to this chain are called substituents. Longest Carbon Chain Name meth- = 1 carbon eth- =2 prop- =3 but- =4 pent- =5 hex- =6 hept- =7 oct- =8 non- =9 dec- = 10 undec- = 11 dodec- = 12 Just FYI… 13 trideca- 30 triaconta- 500 pentacta- 7000 heptalia- 14 tetradeca- 40 tetraconta- 600 hexacta 8000 octalia- 15 pentadeca 50 pentaconta- 700 heptacta- 9000 nonalia- 16 hexadeca- 60 hexaconta- 800 octacta- 17 heptadeca 70 heptaconta- 900 nonacta- 18 octadeca- 80 octaconta- 1000 kilia- 19 nonadeca- 90 nonaconta- 2000 dilia- 20 icosa- 100 hecta- 3000 trilia- 21 heneicosa 200 dicta- 4000 tetralia- 22 docosa 300 tricta- 5000 pentalia- 23 tricosa 400 tetracta- 6000 hexalia-  Principal Functional Group = Suffix The principal functional group is used to define the class the compound belongs to e.g. an alkene, alcohol, etc. Determines the suffix of molecule’s name Refer to ‘Families of Organic Compounds’ handout  Basic Naming Rules The IUPAC systematic name of an organic compound can be constructed based on a series of steps and rules: 1. Identification of the principal functional group and substituents 2. Identification of the longest continuous chain containing the principal functional group. 3. Assign locants (i.e. numbers) to the principal functional group and substituents. First Set of Functional Groups: HYDROCARBONS  Hydrocarbons: When an organic molecule is composed only of hydrogen and carbon, it is called a hydrocarbon: _________: Hydrocarbons with single bonds _________: Hydrocarbons with double bond(s) _______: Hydrocarbons with triple bond(s) -Characterized by C-C single bonds -Also known as _________________ -empirical formula = ________  CnH2n+2, n=8 = ______ Properties: -Hydrophobic (does not mix with water and other polar substances) -Generally low boiling points (due to weak London Dispersion Forces) - Longer alkane molecules have higher boiling points Some IUPAC* names of alkanes: ethane propane butane All alkanes have the suffix “____” *International Union of Pure and Applied Chemistry  ALKANES IUPAC naming system: Molecular formula Condensed Structural Formula Name CH4 CH4 methane C2H6 CH3CH3 ethane C3H8 CH3CH2CH3 propane C4H10 CH3CH2CH2CH3 butane C5H12 CH3CH2CH2CH2CH3 pentane C6H14 CH3CH2CH2CH2CH2CH3 hexane C7H16 CH3CH2CH2CH2CH2CH2CH3 heptane C8H18 CH3CH2CH2CH2CH2CH2CH2CH3 octane C9H20 CH3CH2CH2CH2CH2CH2CH2CH2CH3 nonane C10H22 CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3 decane  ALKANES IUPAC naming system: Name the following alkanes: 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9  Substituents: Branches in Chains Not all alkanes are straight chains. Some alkanes have alkyl side groups (alkyl substituents) attached. -CH3 methyl Ex: -C2H5 ethyl -C3H7 propyl methyl group -C4H9 butyl -C5H11 pentyl -C6H13 hexyl -C7H15 heptyl -C8H17 octyl name: IUPAC naming system: For alkanes with side groups… Substituent(s) prefix suffix family Branches Number of carbons in the longest chain Ex: 2-methylbutane  Assigning Locants (i.e. numbering) The numbers that define the positions of the principal functional group and substituents are called locants. Compounds are numbered from one end of the longest continuous chain. The locants are assigned such that the principal functional group gets the lowest possible locant IUPAC naming system: Name the following branched alkanes 1 2 3 4 5 1 2 3 4 5 2-methylpentane 3-methylpentane When there is ambiguity, the substituent must be numbered according to the carbon atom that it is attached to (aim to get the lowest possible number) First Point of Difference: Which name is incorrect? 1 2 3 4 5 5 4 3 2 1 2-methylpentane 4-methylpentane Aim for the lowest possible number when counting. For alkanes with multiple branches of the same kind attached to the main chain…. give each branch a number. list the numbers in ascending order. give the branch name a multiplying prefix (i.e. di, tri, tetra, etc.) to indicate the number of identical branches. put commas between numbers, and hyphens between numbers and letters. No space! Ex: 4,6-dimethylhept ane  IUPAC naming system: Name the following branched alkane 1. Find the longest continuous chain CH3 - CH - CH3 of C atoms | (parent chain) CH3 - CH - CH2 2. Identify any | substitutents CH3 IUPAC naming system: For alkanes with multiple, but different kinds of branched groups… name the branched groups in alphabetical order. give the branch name a number to indicate which carbon in the main chain it is bonded with. put commas between numbers, and hyphens between numbers and letters. Ex: 4-ethyl-6-methylhept ane  CH3 | CH2 - CH2 | CH2 - CH - CH2 - CH3 | CH - CH3 | CH3  Numbering (con’t) If numbering a functional group results in a "tie" then the first point of difference rule. The first time a difference in numbering occurs, then the method that gives the lower number at this first difference is used. In the event that there is no first point of difference then alphabetisation is used. IUPAC naming system: Name the following branched alkane The order of substituents in the name is based on alphabetical order Drawing alkanes: 3 types of diagrams—all showing the same molecule Structural diagram Condensed diagram CH3CH2CH2CH2CH2CH3 Line diagram Drawing alkanes: Line diagrams: 2 4 6 1 3 5 Every end or point on a line diagram represents a carbon atom. Hydrogen atoms are not shown. Drawing alkanes: Draw the following alkanes using line diagrams 2-methylbutane 3-ethyl-3,4-dimethylheptane  Nomenclature of Alkanes Write the structure of 3-ethyl-2-methylpentane.  No First Point of Difference In the event that there is no first point of difference then alphabetisation is used to determine numbering. Name this alkane: 3-ethyl-6-methyloctane 2 4 8 NOT 1 7 3 5 6 7 1 6-ethyl-3-methyloctane 5 8 6 4 3 2 Two branches occur at C-3 and C-6, regardless of how the parent chain is numbered  2 4 8 1 7 3 5 6 7 1 5 8 6 4 3 2 This time, there is a first point of difference at C-4 6-ethyl-3,4-dimethyloctane  Condensed Diagrams Bonds are (usually) not drawn. Only atoms are drawn Entire molecule is written in one line (even branches) Repeated fragments are simplified with brackets Branches are also indicated with brackets. Structural diagram Condensed diagram CH3CH2CH2CH2CH2CH3 CH3(CH2)4CH3 Condensed diagram  CH3 | CH2 - CH2 | BE CAREFUL! A bracket to CH2 - CH - CH2 - CH3 indicate a branch can be easily confused with a repeated | fragment. Typically brackets such as (CH3) indicate a CH - CH3 branch, while brackets such as | (CH2) indicate a repeated fragment that’s part of a main CH3 chain 1 2 3 4 5 6 7 CH3CH(CH3)CH(CH2CH3)CH2CH2CH2CH3 CH3CH(CH3)CH(CH2CH3)(CH2)3CH3  It is common practice to draw the multiple bond in the condensed formula, but the bond can be omitted when its placement will be obvious OH O Br O CYCLOALKANES -Ring-like structures of alkanes -empirical formula = CnH2n  CnH2n, n=6 = C6H12 IUPAC naming system: Name the following alkanes: cyclobutane cyclooctane cyclopentane The prefix “cyclo” is added to the alkane name IUPAC naming system: Name the following alkanes: CH3CH2CH2 CH CH2 CH2 CH2 propylcyclobutane Numbering the lcoation is not required, since the number is implied  3 3 1 1 1 1 3 3 If there are several substituents, the numbering of ring carbons then continues in a direction (clockwise or counter-clockwise) that affords the second substituent the lower possible location number If two different substituents are present on the ring, they are listed in alphabetical order, and the first cited substituent is assigned to carbon #1.  2 3 1 4 6 5 The disubstituted carbon becomes #1 because the total locator numbers are thereby kept to a minimum. The methyl substituent is then located on carbon #2 (clockwise numbering), and the ethyl group is located on #4 IUPAC naming system: Draw the following alkanes using line structures: 1,1-dipropylcyclopropane 1-ethyl-1,2,5-trimethylcyclopentane HALOALKANES -Alkanes with halogen atoms -Also known as alkyl halides IUPAC naming system: Halogen groups: -F fluoro -Cl chloro -Br bromo -I iodo Just like alkyl substituents, the halogens are placed at the beginning of the name, and are ordered alphabetically. IUPAC naming system: Name the following haloalkanes: STRUCTURAL ISOMERS Compounds with the same molecular formula but with different bonding arrangements are structural isomers. Butane isomers Pentane isomers Ex: Structural isomers of hexane + boiling points Changing the structure affects the boiling point This structure can easily stack and form more London Dispersion Forces with neighbouring hexane molecules Draw all of the structural isomers of heptane using line structures: The longer the chain, the greater the number of structural isomers Number of Carbon Atoms Number of Isomers 4 2 5 3 6 5 7 9 8 18 9 35 10 75 12 355 15 4347