Bonding in Hydrocarbons Alkanes Organic Compounds Bonding in Hydrocarbons Naming Alkanes Empirical Formulae
biology…is that everything that animals do, “The most important hypothesis in all of biology…is that everything that animals do, atoms do. In other words, there is nothing that living things do that cannot be understood from the point of view that they are made of atoms acting according to the laws of physics.” Richard Feynman (1918-1988)
Organic Compounds Mainly contain carbon, oxygen, hydrogen Found in living organisms hence the name organic compounds. Huge implication in life sciences, medicine, biology, chemistry and many areas (such as winery) ~~~
Alkanes Contain C and H only Contain single bonds C-C Have 4 bonds to every carbon (C) atom Are nonpolar
Complete Structural Formulas Show the bonds between each of the atoms H H H C H H C H CH4 , methane In methane, CH4 the four valence electrons of carbon are shared with the single electrons of four hydrogen (H) atoms. Each pair of electrons is a single bond, which can be drawn as a line. When a structure is drawn to show each bond, it is called a complete structural formula.
More Alkanes H H Condensed Structural Formulas H C C H CH3 CH3 H H Ethane H H H H C C C H CH3 CH2 CH3 H H H Propane The complete structural formula for ethane shows the single bonds between two carbon atoms and six H atoms. The complete structural formula of propane shows the 3-carbon chain with single bonds to the attached H atoms. To write a condensed structural formula, the H atoms are written as a group next to their respective C atoms.
IUPAC Names Methane 1 CH4 Ethane 2 CH3CH3 Propane 3 CH3CH2CH3 Name # carbons Structural Formula Methane 1 CH4 Ethane 2 CH3CH3 Propane 3 CH3CH2CH3 Butane 4 CH3CH2CH2CH3 Pentane 5 CH3CH2CH2CH2CH3 The names of organic compounds are determined by the IUPAC rules (International Union of Pure and Applied Chemistry). The stem of the name states the number of carbon atoms in the carbon chain of the compounds. The suffix, in this case –ane, indicates the alkane family.
IUPAC NAMES Hexane 6 CH3CH2CH2CH2CH2CH3 Name # carbons Structural Formula Hexane 6 CH3CH2CH2CH2CH2CH3 Heptane 7 CH3CH2CH2CH2CH2CH2CH3 Octane 8 CH3CH2CH2CH2CH2CH2CH2CH3 Nonane 9 CH3 CH2 CH2CH2CH2CH2CH2CH2CH3 Decane 10 CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3
Mother Eats Peanut Butter Perhaps Her Hair Often Needs Degreasing Methane Ethane Propane Butane Pentane Hexane Heptane Octane Nonane Decane
Naming Branched Alkanes Parent chain is the longest Position of branches is indicated by numbering carbons on parent chain Number from the end that gets branch on lowest number E.g. H-C-C-C-C-C-C-H H H H H CH3H 2-methylhexane Not 5-methylhexane H H H H H H 6 5 4 3 2 1 1 2 3 4 5 6
Naming Branched Alkanes Alkyl gps (side chains) named similarly to alkanes e.g. Methyl, Ethyl etc… More than one alkyl gp – di, tri, tetra Numbers indicate position. Commas between numbers Hyphen between number and letter E.g. 2,2-dimethylbutane H-C-C-C-C-H H CH3H H H CH3H H
Cycloalkanes CnH2n Carbons joined together in rings Saturated homologous series (differ by number of CH2 units) CnH2n
Structural Isomers Same molecular formula but different arrangement of atoms. E.g. C4H10
Practice Now watch this Draw as many structural isomers as you can for: C6H14 (5) C8H18 (18) Now watch this
Empirical Formula The simplest whole number ratio of atoms of elements in a particle of a compound. Can calculate empirical formula from the percentage composition by mass or ratio of constituent elements – of a compound
Empirical Formula The ratio by mass can be converted to ratio by moles if the percentage figures are divided by the respective molar masses. To calculate the ratio of numbers of atoms in the empirical formula, divide all the mole ratios by the smallest mole ratio If one or more figures are decimals or fraction, multiply all figures by 2 or 3 or 4 etc. until the simplest whole numbers are produced.
Eg calculating empirical formula Calculate the empirical formula of a compound of carbon and hydrogen containing 81.8% carbon and 18.2% hydrogen.