Organic ChemistryChapter 14

Science 10CT03D04Resource: Brown, Ford, Ryan, IB Chem

Organic “Carbon” Chemistry

Chemistry for you, Lawrie Ryan Chapter 13

Pages 159-177 Hydrocarbons, Fossil Fuels, Distillation of

Crude Oil, Cracking, Plastics, Polymers Chapter 14

Pages 178-185 Alcohols, Isomers, Ethanol, Alcohol

Reactions, Carboxylic Acids

Formula Name

CH4OH Methan-1-olC2H5OH Ethan-1-olC3H7OH Propan-1-olC4H9OH Butan-1-olC5H11OH Pentan-1-olC6H13OH Hexan-1-olC7H15OH Heptan-1-olC8H17OH Octan-1-ol

14.1 - Alcohols

14.1 - Alcohols Ethanol, C2H5OH is what we find in beer,

wine, and spirits Methanol, if ingested, can be toxic and leads

to blindness The addition of an –OH group to a

hydrocarbon increases the boiling point and the solubility in water: hydrogen bonds

14.2 - Structural Isomers Different arrangements of the same atoms

make different molecules Molecular formula shows the atoms that are

present in a molecule, but gives no information on how they are arranged. Consider, for example, C4H10

Each isomer is a distinct compound, having unique physical and chemical properties.

Structural Isomers of Alkenes

Isomers (although similar) have different physical and chemical properties Propan-1-ol , BP 97.5oC Propan-2-ol, BP 82.5oC

14.3 – Making ethanol (1) Ethanol can be made through fermentation of

simple sugars such as glucose Ethanol can be used to make alcoholic

beverages Yeast, water, sugar, and flavorings are added

in a series of steps. The ethanol, which is what makes the drink

alcoholic, is made when the yeast feeds on sugar in the absence of oxygen (anaerobic respiration)

C6H12O6 2 C2H5OH + 2CO2

14.3 – Ethanol from alkene (2)

There are five main reactions that can take place with alkenes (slides to come) and one of them allows for the formation of an alcohol.

+ H2O

This compound is simply an intermediate

14.3 – Which method is best?

We can make ethanol from fermentation of carbohydrates (C6H12O6) or from the addition of water to ethene (C2H4). Which process is best? Ethanol from ethene requires crude oil

supplies which are in short supply. Cheap for now!

In Brazil where no natural oil supplies exist, they have relied on the manufacturing of ethanol through fermentation to fuel cars along with petrol. Sugar cane is used in this case.

14.4 – Reactions of alcohols

Combustion of alcohols is simple as they are flammable. Alcohols are often added to petrol to make them easier to ignite

Oxidation is common, especially in wine and beer. The taste changes as its left exposed to oxygen in the air. Wine tastes sharp or sour after this process as the ethanol has been converted to ethanoic acid (acids taste sour, think citrus).

14.5 – Carboxylic Acids We will not be dealing with carboxylic acids in

this unit, but materials with this functional group have many uses and applications.

14.6 – Reactions with Ethene

This section is not in your book, but is very important.

As discussed, ethene is much more reactive than ethane due to the presence of the double bond

There are five major reactions for ethene1. Formation of alkanes2. Formation of alcohols (mentioned earlier)3. Formation of halogenalkanes4. Formation of dihalogenalkanes5. Formation of polymers (discussed in Ch.

13)

14.6 - Alkenes General formula is CnH2n Alkenes are unsaturated hydrocarbons

containing a carbon-carbon double bond

The double bond can be broken resulting in a new bonding site on each carbon atom.

Alkene addition with Hydrogen

With the presence of a nickel catalyst at about 150oc, for example

Known as hydrogenation, used in the margarine industry to convert oils containing unsaturated hydrocarbon chains into more stable saturated compounds with higher melting points

CH3CHCH2 + H2 ----> CH3CH2CH3

Ni catalyst propene hydrogen gas propane

14.6 - Alkene addition with water

The reaction with water is known as hydration and converts the alkene into an alcohol.

Use of concentrated sulfuric acid as catalyst. Involves intermediate in which H+ and HSO4

- ions are added across the double bond.

H2SO4 (conc) H2OCH2CH2 CH3CH2(HSO4) CH3CH2OH + H2SO4 ethene ethyl hydrogen sulfate ethanol

H 2SO 4

needed

H2O +

14.6 - Alkene addition with

hydrogen halides Hydrogen halides (HCl, HBr, etc) react with

alkenes to produce hydrogenalkanes. Take place rapidly in solution at room

temperature. All halogens are able to react in this manner,

but the reactivity is in the order HI>HBr>HCl, per the decreasing strength of the hydrogen halide bond.

CH2CH2 + HCl ----> CH3CH2Cl

ethene chloroethane

14.6 - Alkene addition with halogens

Halogens react with alkenes to produce dihalgeno compounds.

Occur quickly at room temperature and are accompanied by the loss of color of the reacting compound.

CH3CHCH2 + Br2 ----> CH3CHBrCH2Br

propene bromine gas 1,2-dibromopropane

14.6 - Polymerization of alkenes

Since alkenes readily undergo addition reactions by breaking their double bonds, they can be joined together to produce long chains known as polymers. The alkene is known as the monomer.

Example: Ethene polymerizes to form polyethene,

commonly known as polythene. First discovered by accident in 1935, was used extensively as an insulator in the WWII.

14.6 - Repeating Units for Polymers

Poly(ethene): Insulator, water tanks, piping..

Poly(propylene): Manufature clothing, especially thermal

wear

14.6 - PVC (poly vinyl chloride)

Poly(chloroethene) (PVC) is widely used in construction materials, packaging, electrical cable sheathing, etc.

Synthesis is associated with toxic byproducts known as dioxins, which are linked to reproductive disorders and a variety of cancers.

14.6 – Distinguishing between Alkanes and

Alkenes Alkenes readily undergo addition reactions,

alkanes will not (only in UV light) Shake separate samples of alkanes and

alkenes with bromine water at room temperature, red-brown color of bromine water is decolorized by the alkene (but not the alkane)

Color of a burned flame. Alkenes have high ratio of C:H and leave unburned carbon. Results in a smokier, dirtier flame from alkenes.