Unit M: Organic Chemistry



Unit 2: Organic Chemistry (Hebden-Unit X p.213)

Warm Up Questions, Org Bkt p.26#1-3

Introduction

Def: Chemistry of carbon compounds

Some compounds are produced synthetically, some occur naturally, some are beneficial, some are hazardous.

Where are they found?

Fossil fuels(petroleum by-products, natural gas), all living things (trees, grasses, vegetables, insects, animals, people)

Petrochemicals industry: largest industry involving organic chemistry

Petroleum is separated through fractionated distillation for every day use’s products such as foods, cosmetics, plastics, clothing fibres, pharmaceuticals and fuels.

Carbon is tetravalent, it has a valence of 4 and can form:

.4 single bonds (alkanes)

.1 double bond and 2 single bonds (alkenes)

.1 triple bond and 1 single bond (alkynes)

Hydrocarbons: containing only carbon and hydrogen atoms.

.simplest type of organic compounds

There are 6 ways to represent an hydrocarbon formula:

Let’s use butane molecule (lighter fuel) as an example (Edvantage p.403, 405)

Table 8.1.2, Org Bkt p.27

|1) Molecular formula |C4H10 |

|2) Structural formula | H H H H |

| || | | | |

| |H-C-C-C-C-H |

| || | | | |

| |H H H H |

|3) Condensed structural formula |CH3-CH2-CH2-CH3 |

|4) Carbon skeleton formula | C C |

| |/ \ / or |

| |C C |

|5) Ball and stick model |Org Bkt p. 27 |

| | |

|6) Space filling model |Org Bkt p.27 |

| | |

Practice Problem#1- Org Bkt p.28 (Using Structural Formulas EI p.40)

Org Bkt p.30#1

There are 5 types of hydrocarbons (contains hydrogen and carbon):

alkanes, cycloalkanes, alkenes, alkynes, and aromatic compounds.

1) Alkanes

They contain only single bonds.

They are saturated, meaning that there is no room for other atoms to combine with the carbon skeleton.

General formula: CnH(2n+ 2)

Naming: compound ends in “-ane”

|#C |1 |2 |

|methoxymethane |Aerosol spray propellant | O |

|(dimethyl ether) | |/ \ |

| | |H3C CH3 |

|Ethoxyethane |Early anesthetic |H3C O CH3 |

|(diethyl ether) | |\ / \ / |

| | |CH2 CH2 |

|Methoxybenzene |Anise (licorice) flavoring |Draw structure |

|(methylphenyl ether) | | |

O

II

d) Aldehydes: R-C-H

Organic compound containing a carbonyl group at the end of the carbon chain.

A carbonyl group is a carbon atom double bonded to an oxygen atom.

Uses: dyes, organic acids, formaldehyde (biological preservative)

O

II

Aldehyde group: - C - H

NB: You do not need to know how to name aldehydes.

Examples:

O

II

H – C - H formaldehyde (common name), methanal

CH3 – CHO ethanal

CH3 – CH2 – CH2 – CH – CHO 2-methylpentanal

I

CH3

benzaldehyde

O

e) Ketones: ||

C

/ \

R R’

Organic compound containing a carbonyl group at a position other than at the end of a hydrocarbon chain.

Uses: as solvents, to make polymers, Nail polish remover: acetone

Polymer: a very large molecule that is produced by linking together many smaller molecules.

NB: You do not need to know how to name ketones.

Examples:

O

II

C or CH3COCH3 acetone(common name), propanone

/ \

H3C CH3

O

||

H3C C 3-hexanone

\ / \

CH2 CH2 -CH2 -CH3

cyclohexanone

Quick Check #5, Org Bkt p.32

O

f) Carboxylic Acids: ||

R--C

\

O- H

Compound containing a carboxyl (-COOH) group

Uses: organic acids, food preservatives

Unpleasant odour, vinegar…

NB: You do not need to know how to name most carboxylic acids.

O

II

C

/ \

R OH

Examples:

CH3COOH Acetic acid (common name), ethanoic acid

HCOOH Formic acid (common name), methanoic acid

Found in red ant venom, fourmis (French)

CH3-CH2- CH2- COOH Butyric acid (common name), butanoic acid

Responsible for odour of smelly feet

Cat’s pheromones: when cat rubs its cheeks on your leg, you’re being marked as safe territory.

Cat’s facial secretions: mix of fatty acids including oleic acid, azelaic acid, pimelic acid, palmitic acid, butyric acid, caproic acid, 5-aminovaleric acid, para-hydroxyphenylacetic acid and trimethylamine.

O

||

g) Esters: C

/ \

R OR’

Compound in which a –COO- group joins 2 hydrocarbon chains

Uses: Strong fruity odours, used in perfumes and flavorings

DNA, some plastics and explosives.

NB: You do not need to know how to name esters.

H3C CH3CH2CH2

\ \

C=O C=O

/ /

CH3CH2CH2CH2CH2CH2CH2CH2O CH3CH2O

Octyl acetate (orange flavoring) ethyl butanoate(pineapple flavouring)

Ester Synthesis:

Reaction an organic acid (carboxylic) and an alcohol in the presence of an inorganic acid such as HCl or H2SO4.

Acetic acid methanol methyl acetate water

O O

II II

CH3 – C- O –H + CH3 -OH → CH3 – C- O – CH3 + H2O

Demo: Ester Preparation

Few ml of carboxylic acid + few mL of alcohol + few drops of acid + heat

h) Amines: R-NH2 or R-NH-R’ or R-N-R’ Nitrogen is trivalent

|

R’’

Compound containing only single bonds and a nitrogen atom is attached to a carbon atom.

Uses: dyes and drugs,

chlorpheniramine (antihistamine)

ephedrine, phenyllephrine: decongestants.

Have “fish-like” odour

NB: You do not need to know how to name amines.

Examples

CH3-NH2 methylamine

H3C CH3 dimethylamine

\ /

N

|

H

i) Amides:

Compound containing a nitrogen atom bonded to a carbonyl group.

O

II

C R’’

/ \ /

R N

|

R’

Uses: plastics, rubber, inks, cosmetics, nylon, Kevlar

Acetominophen: pain killer

Amide group linking amino acids together in a peptide chain that makes up proteins.

NB: You do not need to know how to name amides.

Examples:

O

|| ethanamide

C

/ \

H3C NH2

O

|| butanamide

C

/ \

CH3CH2CH2 NH2

Quick Check#6, Org Bkt p. 33

j) Amino Acids:

Compound that contains carboxylic acid and amine groups

20 amino acids: building blocks essential to life

Example:

CH3- CH – COOH 2-aminopropanoic acid (common name: alanine)

I

NH2

2 important properties of amino acids:

a) Highly soluble in water

b) Link with other amino acids to form dipeptides and polypeptides forming proteins.

O O O O

II II II II

H–N-CH2-C-OH + H-N-CH2-C-OH → H–N-CH2-C- N-CH2-C-OH + H2O

I I I I

H H H H

a “dipeptide”

k) Summary of Functional Groups

Table 8.2.3, Org Bkt p.34

Heb p. 240-241#37

Review Questions 8.2, Org Bkt p.35-37

l) Reactions of Organic Molecules

(i) Warm Up

1) Unsaturated fats such as those found in olive oils and avocados are healthier than saturated fats found in coconut oil and butter. What do the words “unsaturated” and “saturated” mean in terms of organic molecular structure?

Answer: unsaturated means the presence of a double bond while saturated means the absence of a double bond

2) Earlier in this unit, you learned about the types of chemical reactions. What are the products of the combustion of a hydrocarbon or carbohydrate?

Answer: carbon dioxide and water

3) The chemical reactivity of an organic compound largely depends on the type of organic compound involved. Match the functional group in the column on the left to the correct description from the column on the right. Draw lines to connect each pair.

(a) alcohol (iii) (i) contains a carboxyl group

(b) alkyne (vi) (ii) contains a halogen

(c) carboxylic acid (i) (iii) contains a hydroxyl group

(d) alkyl halide (ii) (iv) contains a double bond between 2 carbon atoms

(e) alkene (iv) (v) contains a –COOR group

(f) ester (v) (vi) contains a triple bond between 2 carbon atoms

Examples of Simple Organic Reactions

.Respiration, reproduction, digestion, and circulation

.Production of proteins, carbohydrates, nucleic acid (DNA, RNA)

.Products of organic rxns: fabrics, building materials, food, drugs, paints, fuels, greases, perfumes, explosives, plastics, dyes and soaps.

We will look at the following reactions with organic molecules:

(ii) Combustion Reactions

(iii) Substitution Reactions

(iv) Addition Reactions

(v) Elimination and Condensation Reactions

(vi) Polymerization

(vii) Addition Polymerization

(ii) Combustion Reactions

Hydrocarbon reacting with oxygen, also known as an oxidation reaction.

During a complete combustion, in excess oxygen, the products are water and carbon dioxide.

Ex: combustion of octane (car fuel):

2 C8H18(l) + 25 O2(g) →16 CO2(g) + 18 H2O(g) + Energy

During an incomplete combustion, there is a limited amount of oxygen and the products may be carbon monoxide or carbon and water.

Carbon: solid, sooty material present in blackened smoke

CO: colourless, odorless and very poisonous gas.

( It is dangerous to run a car in an enclosed space such as a garage.

Example of complete combustion:

2 CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(g) + Energy

Example of incomplete combustion:

CH4(g) + O2(g) → C(s) + 2H2O(g) + Energy

or

2 CH4(g) + 3 O2(g) → 2 CO(g) + 4 H2O(g) + Energy

Quick Check#7: (E.I. p.431)

1) Some cars are powered by propane. Write the balanced chemical equation for the complete combustion of propane.

C3H8 + 5O2 ( 3CO2 + 4H2O + energy

2) Find out if your home has a carbon monoxide detector. Why might a carbon monoxide detector be a good idea?

A carbon monoxide detector might indicate the presence of toxic carbon monoxide obtained for incomplete combustion in a fireplace or in candles.

3) Write a balanced chemical equation to represent the incomplete combustion of propane.

C3H8 + 2O2 ( 3C + 4H2O + energy

Or 2C3H8 + 7O2 ( 6CO + 8H2O + energy

(iii) Substitution Reactions

An atom from a reactant takes the place of an atom on an organic molecule.

Ex: When exposed to ultraviolet light (catalyst), methane reacts with chlorine to produce chloromethane.

H H

| |

H – C + Cl-Cl → H – C + H-Cl

/ \ / \

H H H Cl

One hydrogen atom is replaced by a chlorine atom.

NB: Carbon remains tetravalent.

This reaction can go further when another chlorine atom replaces a hydrogen atom and, produces dichloromethane.

CH3Cl + Cl2 → CH2Cl2 + HCl

Drawing on the board.

Aromatic compounds can also undergo substitution reactions. p.432 (EI) fig 8.3.2

Ex: benzene + chlorine → chlorobenzene + hydrochloric acid

Ex: chlorobenzene + chlorine → dichlorobenzene + hydrochloric acid

Drawing on the board.

(iv) Addition Reactions

When an unsaturated compound becomes saturated.

A double bond becomes a single bond.

A triple bond becomes a double bond.

General Equation:

H H H H

\ / | |

C=C + X-Y ( H – C – C - H

/ \ | |

H H X Y

Halogenation: Halogens reacting with alkenes and alkynes.

H H Cl Cl

\ / | |

C=C + Cl-Cl ( H –C – C -H

/ \ | |

H H H H

Ethanol is a common additive to gasoline and is synthetically produced by adding ethene(ethylene) and water in the presence of a catalyst: phosphoric acid or sulfuric acid.

H H H H

\ / H3PO4 | |

C=C + H-O-H ---------( H-C – C – O – H

/ \ or H2SO4 | |

H H H H

Hydrogenation: Adding hydrogen atoms to the unsaturated site.

H H H H

\ / Ni | |

C=C + H-H ---------( H -C – C – H

/ \ catalyst | |

H H H H

Alkynes can also undergo addition reactions:

Br Br Br Br

| | | |

HC Ξ CH + Br2 ---------( C = C + Br2 -----( H – C - C - H

| | | |

H H Br Br

Quick Check #8 (EI p.434)

1) How can the number of atoms bonded to the carbon assist your classification of a reaction as addition or substitution?

Carbon is always tetravalent

A triple bond will become double bond, and a double bond will become saturated

2) Classify the following as substitution or addition reactions:

a) H3C-CH3 + Br2 ---------( H3C-CH2 + HBr addition

|

Br

b) H3C CH3 Cl

\ / |

C=C + HCl ---------( H3C-CH2-CH-CH3 substitution

/ \

H H

3) Using structural formulas, draw reactions showing the following. For each reaction, write the ame of the reactants and products under the appropriate molecule.

a) Formation of bromoethane

H H H H

\ / | |

C = C + HBr ( Br – C – C - H

/ \ | |

H H H H

b) Reaction between trichloromethane and fluorine

Cl Cl

| |

Cl – C – Cl + F2 ( Cl – C – Cl + HF

| |

H F

4) Can an alkane undergo an addition reaction? Explain.

No, because an alkane is not unsaturated.

(v) Elimination Reactions

An elimination reaction is the opposite of an addition reaction. A small molecule such as H2O or HX is eliminated.

H Br H H

| | alcoholic \ /

H - C –C – H ---------( C = C + HBr (H and Br are eliminated)

| | KOH / \

H H H H

NB: In an elimination reaction, the number of atoms that a carbon atom is bonded to, decreases. In the above reaction, each carbon atom in the reactant is bonded to four other atoms. In the products, each carbon atom is only bonded to three other atoms.

Dehydration or condensation reaction: if water is eliminated (dehydration) or produced (condensation).

(EI p.435: fig 8.3.10)

Esterification: process of reacting an organic acid and an alcohol to produce an ester. This is a type of dehydration or elimination reaction.

(EI p.435: fig 8.3.10)

The –OH group on the carboxylic acid combines with the H atom from the alcohol group to make water. The name of the ester is derived from the names of the alcohol and carboxylic acid. The first part of the name comes from the alcohol. The alcohol portion of the ester is named by removing the “-ol” ending and changing it to “-yl”. The name of the carboxylic acid part is changed by dropping the “-oic acid” part and adding “-oate”.

Ester example: ethyl butanoate (sweet pineapple smell)

Produced when ethanol and butanoic acid are reacted:

Butanoic acid + ethanol ( ethyl butanoate + water

(EI p.435: fig 8.3.11)

Animal and vegetable fats and oils are esters.

Saturated fats: molecules where the organic acid part of the carbon chain does not contain any double bonds.

Unsaturated fat: contains double bonds in the carbon parent chain.

Fats: important nutrient for your body where they supply energy and help in the absorption of fat-soluble vitamins. (Vitamins A,D,E,K)

People on a Mediterranean diet (fruits, vegetable, fish and whole grains) consume more unsaturated fats than saturated fats. This could be a reason why people on this diet have healthier lives.

Sample Problem: Writing Equations for Simple Organic Reactions, Org Bkt p.38

Ex: Reaction between methanol and acetic acid where the product is airplane glue.

Practice Problems: Writing Equations for Simple Organic Reactions

1) Oil of wintergreen contains the ester formed when methanol and salicyclic acid react. What is the name of the ester responsible for this pleasant odor?

Answer: Methyl salicylioate

2) Ehtyl heptanoate smells like apricots. Draw structural diagrams to represent the reaction that produces ethyl heptanoate.

3) Cholorofluorocarbons (CFCs) in the stratosphere are molecules that use up Earth’s protective ozone layer. Ozone molecules at this level absorb harmful UV-B and UV-C radiation. One such CFC is called chlorodifluoromethane. Draw structural diagrams to represent how this CFC is produced. Assume that methane reacts with chlorine, and then the product reacts with excess fluorine. What type of reactions are these?

H H F

| | |

H – C – H + Cl2 ( H – C – Cl + F2 ( F – C – Cl

| | |

H H H

Reaction Type: Substitution

(vi) Polymerization, Org Bkt p.38

Macromolecules: very large molecules containing tens of thousands of atoms each.

Polymers are long molecules made by stringing together smaller parts called “monomers”.

Polymer: many parts Monomer: one part

Natural polymers: DNA, starch, proteins, celllulose, rubber, silk

Synthetic polymers: plastics, nylon, styrofoam, pharmaceuticals, Teflon, paints, Plexiglas

Cellulose: several hundred to over ten thousand glucose molecules linked together

The name of a polymer depends on the monomer that it was made from.

We represent a polymer by showing the monomer in brackets, with “n” representing some large number of repeating units.

Homopolymer: one repeating monomer

Ex: vinylidene ( polyvinylidene (EI p.438 fig 8.3.14)

Copolymer: mixture of repeating units. (EI p.438 fig 8.3.15)

Addition Polymerization

Polyethylene: most common plastic

.Formation of polyethylene: repeating units of ethylene

H H

\ /

n C=C ethylene

/ \

H H

( polymerization

H H H H H H H H H H H H

| | | | | | | | | | | |

R – C – C – C – C – C – C – C – C – C –C – C – C –R

| | | | | | | | | | | |

H H H H H H H H H H H H

H H

| |

Simplified: - C – C - where n = a very large integer

| |

H H n

HDPE (high-density polyethylene): linear carbon backbone with few branches.

Such long strands of these molecules fit very closely together.

LDPE(low-density polyethylene): the carbon backbone has many polyethylene branches and these chains of polymer cannot be packed tightly together.

Ex: Rayon/viscose(artificial silk) is a long chain of glucose molecules broken into shorter chains.(regenerated cellulose)

| |HDPE |LDPE |

|Properties |Stronger and stiffer |Softer, films |

|Examples |Milk jugs, plastic garbage cans, shampoo bottles, water pipes |Plastic films, food wrap, garbage bags |

UHMWPE (ultra-high molecular weight polyethylene): bulletproof vests, artificial joints Molar Mass (MM): millions of gram/mol

Polyethylenes are thermoplastic since they can be melted and molded into other shapes.

Polyethylenes are not biodegradable and should be recycled.

Examples of Polymers Formed by Addition Reactions

|Name |Formula |Monomer |Applications |

|Polypropylene |-[CH2-CH(CH3)]n- |Propylene |Carpet (indoor/outdoor) |

|(PP) | |CH2 = CHCH3 |Plastic bottles, Upholstery |

|Poly(vinyl |-(CH2-CHCl)n- |Vinyl chloride |Pipes, Siding, Flooring |

|chloride) | |CH2 = CHCl | |

|(PVC) | | | |

|Polystyrene |-[CH2-CH(C6H5)]n- |Styrene |Insulation, Furniture, Car’s Bumper, |

|(PS) | |CH2 = CHC6H5 |Packing Materials |

|Polytetrafluoro-ethylene |-(CF2-CF2)n- |Tetrafluoroethylene |Non-Stick Surface on Cooking |

|(PTFE, Teflon) | |CF2=CF2 |Ustensils, Engines’ Lining, |

| | | |Electrical Insulation |

|Polychloeoprene |-[CH2CH=CCl-CH2]n- |Chloroprene |Synthetic rubber products for |

|(cis + trans) | |CH2CH=CCl=CH2 |wetsuits, insulation |

|(Neoprene) | | | |

Starch: mixture of 2 polymers; amylose(straight chains) and amylopectin(many branches) of shorter glucose(C6H12O6) chains.

Modified starch:

.obtained by treatment with acids, enzymes or oxidizing agents

.approved food additive

.used to thicken sauces

.prevent French dressing from separating

.fat substitute

.drying agent

Quick Check #9 (EI p.440)

1) Polytetrafluoroethylene, commonly called Teflon, is a non-stick substance used in kitchen products, the aerospace industry, electronics, and communications. It is a polymer that can b represented by the diagram below.

Is this a homopolymer or a copolymer? Homopolymer(repeating monomer)

Circle the repeating unit on the diagram

F F F F F F F F F F F F

| | | | | | | | | | | |

… C – C – C – C – C – C – C – C – C – C – C – C …

| | | | | | | | | | | |

F F F F F F F F F F F F

2) On a molecular level, how does HDPE differ from LDPE?

HDPE: long molecular strands

LDPE: several branches of molecules

3) Many plastics pipes, siding, and flooring are made of polyvinyl chloride or PVC. The reaction for its formation is shown below. What type of reaction is this? On the diagram below, circle the repeating unit in this polymer.

Cl H Cl H Cl H

\ / \ / \ /

C = C + C = C + C = C

/ \ / \ / \

H H H H H H

(

Cl H Cl H Cl H

| | | | | |

- C – C – C – C – C - C –

| | | | | |

H H H H H H

4) The symbols shown here are used to distinguish HDPE from LDPE. List two products in your home that are made up of HDPE and two products made up of LDPE.

| |HDPE |LDPE |

|Examples |Shampoo bottle |Garbage bag |

| |“Thick” Water bottle |Food wrap |

Condensation Reactions

1) Nylon Production:

Hexamethylenediamine reacts with adipic acid. For each amine that reacts with a carboxylic acid, water is eliminated. The monomer is highlighted.

H H O O H H O

| | || || | | ||

- N – (CH2)4 – N – C – (CH2)4 – C – N – (CH2)4 – N – C - (CH2)4

2) Protein Production

Building block: amino acids

Amino acid: organic molecule containing at least one amino group (-NH2) and one carboxyl group (-COOH).

In our body: 20 different amino acids

How?

When an amino group on one amino acid reacts with the carboxyl group of another amino acid.

Dipeptide: When two amino acids combine

amino acid + amino acid ( dipeptide + water

Fig 8.3.19, Org Bkt p.39

Polypeptide (protein): many amino acids combine. A water molecule is eliminated with the formation of a new peptide bond.

Protein: natural polymer

H R H R H R H R H R

| | | | | | | | | |

N – CH – C – N –CH – C – N – CH…- C – N – CH – C – N – CH –COOH

|| || || ||

O O O O

DNA or RNA: natural proteins

DNA: deoxyribonucleic acid, largest molecules known

Activity 8.3: Organic Molecules In Every Day Life, Org Bkt p.39-Optional

8.3 Review Questions #1-12, Org Bkt p.40-41

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