Topic 10 – Organic Chemistry 10.1 - Fundamentals of Organic Chemistry 1

Organic Chemistry What do you know about organic chemistry? Discussion 2

Organic Chemistry Organic Chemistry – the study of carbon –based compounds. Why carbon? Can bond up to four times. Can undergo catenation (create long chains of itself) Can form straight-chain, branched, or cyclical structures. 3

General Formula – CnH2n+2 Classification Homologous Series – group of compounds with the same general formula, structure, physical and chemical properties. Examples: ALKANE METHANE ETHANE PROPANE BUTANE FORMULA CH4 C2H6 C3H8 C4H10 General Formula – CnH2n+2 *** Alkanes only have single C-C bonds and differ by the number of methylene groups. Alkenes have C=C bonds, and alkynes have C C bonds. Homologous series can also contain functional groups. 4

Exercise Using the molecular model kits, build a molecule for: CH4 C2H6 C3H8 C4H10 C5H12 C6H14 Draw each of the molecules.

Physical Properties Properties change as more atoms are added. Example: boiling point goes up with every additional carbon due to increased intermolecular forces. Distillation can be used to separate compounds based on their boiling points. 6

Intermolecular Forces There are three kinds of intermolecular forces that occur between molecules. They are listed here in order of increasing strength: London dispersion forces (between non-polar molecules) Dipole–dipole forces (between polar molecules) Hydrogen bonding (between hydrogen of one polar molecule and O, N, F of another polar molecule) London forces and dipole-dipole forces are collectively known as “van der Waal forces.”

London Dispersion Forces Instantaneous dipole that occurs accidentally in a given atom induces a similar dipole in a neighboring atom. Significant in large atoms/molecules. Occurs in all molecules, including nonpolar ones.

London Forces The magnitude of London forces are affected by three factors. Number of electrons Size (volume) of the electron cloud Shapes of the molecules

Dipole–Dipole Attraction Polar molecules contain different atoms which have different electronegativities and can be thought to be like a small bar magnet. Oppositely charged ends attract and like ends repel. Molecules organize themselves to maximize the attractive forces and minimize repulsive forces giving molecules unique shapes.

Hydrogen Bonding in Water Blue dotted lines are the intermolecular forces between the water molecules.

Homework Complete Structural Formula Worksheet

Think, Pair, and Share Discuss and determine how you think these intermolecular forces will affect the physical properties (melting point, boiling point, vapor pressure) of the molecules you built in the previous exercise: CH4 C2H6 C3H8 C4H10 C5H12 C6H14

Physical Properties 1414

Physical Properties This trend in boiling point results from increasingly strong London forces as the carbon chain becomes longer. Fractional distillation is a physical separation process that uses differences in boiling points to separate the mixture into fractions of similar boiling point. 15

Chemical Formulae Many ways to represent an organic compound: Lewis dot structure Empirical formula Molecular formula Structural formula Full – shows all atoms and bonds Condensed – shows all atoms, no bonds Skeletal – lines, ends and corners are carbon atoms, only functional groups are identified. CH3CH2COOH 16

Nomenclature The International Union of Pure and Applied Chemistry (IUPAC) is the world authority on chemical nomenclature. The name of a chemical substance needs to provide enough information to identify the class of compound from which the chemical is derived, including any substituents and functional groups present. 17

(longest carbon chain) IUPAC Nomenclature Step 1 – Identify longest carbon chain Step 2 – Determine if there are any branches Step 3 – Number branches with lowest carbon Step 4 – Arrange branches alphabetically Step 5 – Use commas to separate numbers Step 6 – Use hyphen to separate numbers and letters Step 7 – Use multipliers if multiple of one branch is present Step 8 – Successive words merge together Prefixes Parent Chain Suffix Principal Group (alphabetical order) (longest carbon chain) (-ane, -ene, -yne) (functional groups) 18

IUPAC Nomenclature Parent Chain meth - 1 Branch Names eth - 2 pro - 3 bu - 4 pent - 5 hex - 6 Branch Names methyl - CH3 ethyl - CH2CH3 propyl - CH2CH2CH3 butyl - CH2CH2CH2CH3 Example: 3-ethyl-2-methylhexane 6 carbons is the longest chain (hexane) 2 branches (methyl and ethyl) Lowest numbers are 2, 3 19

IUPAC Nomenclature Numbers Structural Isomers mono - 1 di - 2 cis- tri - 3 tetra - 4 penta - 5 Structural Isomers cis- trans- C = C Cl H C = C Cl H Example: 3-ethyl-2-methylhexane 6 carbons is the longest chain (hexane) 2 branches (methyl and ethyl) Lowest numbers are 2, 3 20

5-ethyl-2,3,3-trimethylheptane Nomenclature 5-ethyl-2,3,3-trimethylheptane 21

Nomenclature Draw the structural formula for C2H4O. 22

Nomenclature Draw the structural formula for C2H4O. O H ̶ C ̶ C ̶ H H ethanal 23

Nomenclature Hydrocarbons Saturated – all C-C single bonds Unsaturated – some C=C and C C bonds Can have cyclo (all C-C) and aromatic (C=C) rings Functional groups: Take priority in naming Carbon number is lowest on functional groups 24

Question Predict the order of the boiling points for three isomers of pentane below. Look them up to see if you are right. Using IUPAC nomenclature, name each of them.

Nomenclature Practice HO Cl 26

Nomenclature Practice HO but-2-ene but-1-yne Cl butan-2-ol 4-methylpent-2-yne 2,3-dichloro-4,5-dimethylhexane 1,3-dimethylcyclopentane buta-1,3-diene 27

Nomenclature Practice OH O 28

Nomenclature Practice propanone (ketone) n-butanal (aldehyde) O OH O butanoic acid (carboxylic acid) methyl propanoate (ester) 29

Your Turn Draw the structural formula for C4H8O. 30

Your Turn Draw full structural, condensed structural and skeletal formulas for at least 5 of the C4H8O compounds (no cyclic ones) 31

Your Turn Draw the structural formula for C4H8O. 32

Classifying Molecules Saturated hydrocarbons – organic compounds consisting of carbon and hydrogen atoms only. Carbon-carbon bonds are single bonds. Mostly alkanes, which are aliphatic or straight-chain compounds. Unsaturated hydrocarbons – contain double and/or triple carbon-carbon bonds. Natural compounds – found in plants and animals – synthesized by organisms. Synthetic compounds – mostly man-made compounds. 33

Propane CH3CH2CH3 Alkane Propan-2-ol CH3CH(OH)CH3 Alcohol Propanal NAME FULL CONDENSED SKELETAL SERIES Propane CH3CH2CH3 Alkane Propan-2-ol CH3CH(OH)CH3 Alcohol Propanal CH3CH2CHO Aldehyde Propanone CH3C(O)CH3 Ketone Propanoic acid CH3CH2COOH Carboxylic acid Propene CH3CHCH2 Alkene 3434

Functional Groups Functional Group Name Group double bond RCOOR’ triple bond R ̶ O ̶ R’ ROH RNH2 RNHR RN[R’]R” RCHO RCONH2 RCOR’ RCN RCOOH R ̶

Classifying Molecules Aliphatic compounds – contain straight-chain carbon-carbon bonds. Alkanes – saturated hydrocarbon containing only carbon-carbon single-bonds Alkene – unsaturated hydrocarbon containing carbon-carbon double-bond(s) Alkynes - unsaturated hydrocarbon containing carbon-carbon triple-bond(s) Halide or Halogenoalkane – hydrocarbon containing halogen(s) substituted for hydrogen(s) Alcohol – hydrocarbon containing hydroxyl group(s) (-OH ̶ ) substituted for hydrogen(s) Aldehyde – hydrocarbon containing carbon-oxygen double-bonds on primary carbon Ketones – hydrocarbon containing carbon-oxygen double-bonds on secondary carbon Carboxylic acid – hydrocarbon containing a single primary carbon with a carbon-oxygen double-bond AND a carbon-hydroxyl single-bond 36

Classifying Molecules Cyclic compounds – organic molecules that contain carbon-carbon rings OR OR Aromatic compounds – organic molecules that contain benzene rings OR OR called phenol group in a compound can hydrogenate the double bonds using a catalyst 37

Homework Complete the IUPAC Nomenclature Worksheet