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Macro Molecules

Macro Molecules:

Macro Molecules, are large molecules, made by joining together of many small molecules.

This process of joining together smaller units into a large macro molecule polymer is called polymerization.

Monomer:

Small molecules, that join together to form one large polymer molecules.

There are two kinds of polymer:

Synthetic Polymer

Natural Polymers

Synthetic Polymers:

Synthetic Polymers are manmade polymers that are formed by

• Addition Polymerization – Addition Polymers
• Condensation Polymers – Condensation Polymers

Addition Polymers:

Addition Polymers are made from unsaturated monomers through an addition reaction.

Repeating Unit: Simplest part of the polymer which is repeated many times to form the polymer.

In addition Polymerization any alkene is converted into Poly alkene.

Alkane is converted to Alkane.

Making of Poly Ethene conditions:

Temperature – 200 °C  

Atmospheric Pressure: 1000

Catalyst – Zeigler’s Catalyst  – TiCl₄  +   (C₂H₅)₃ A_l – Mixture of Titanium Tetre Chloride and Tetra Aluminium

Further Advantages of Addition Polymerization:

Perspex – Used in making car windows

Taflon – Used in production of utensils, rain coats and rubber tubings

Polystylene – Disposable glasses and plastics.

Condensation Polymers:

When two different monomers join, each with two functional group. The monomers join their functional groups, by getting rid of or eliminating small molecules.

Condensation Polymers are made from monomers containing alcohol, acid or amino functional groups.

Through elimination of small molecules like H₂O. E.g. Nylon and Teryline.

Nylon/ Polyamide:

It is formed by the combination of Di Carboxylic Acid and Di Amine.

1. Why Nylon also called as Poly Amide – due to presence of Amide Linkage.

Uses of Nylon:

• Nylon is used in making synthetic fibres
• In production of ropes, fishing lines and clothes
• For making rain coats and parachutes.

Terylene / Polyester:

Terylene is formed by the combination of  DiCarboxylic Acid and Diol (Hydroxyl Group).

Uses of Terylene:

• Fabrics – That are strong, resists strechingand sinking. Doesn’t crumple.
• Sleeping bags are made using teryline. Hence they do not shrink (Synthetic Fibre).

Disadvantages of Plastic:

• Plastics are non-biodegradeble, can’t be decomposed by bacteria. Hence they result in polluting the earth.
• Produce toxic gases(HCl) when burnt, this contriburtes to acid rain.
• Plastics are Carbon based polymers – burn easily.
• Plastics that require Chloro-Flouro Carbons (CFC) during production may contribute to global warming when the CFC is allowed to escape. Thus may lead to flodding in low lying areas.

Natural Polymers:

Natural Polymers are formed by condensation polymerization.

Protein:

When two amino acids combine with each other, protein is formed and H₂O is a by-product.

Protein have similar linkage to that of Nylon (amide linkage) –Thus can be called Polyamide.

They are joined together by condensation polymerization.

Each amino acid has an acidic functional group and an amino functional group.

Proteins are possessing the same amide linkages as Nylon but with different monomer units.

Proteins can also by hydrated back into amino acids, by heating them with Sulphuric Acid (H₃PO₄).

This adds water molecules into the polymer.

Hydrolysis:

Is a reaction in which molecules are broken down by reaction with water, in the presence of Alkali or Acid.

The products of the hydrolysis of protein (amino acids) and Carbohydrates can be separated and identifies through chromatography.

The chromatogram needs to be sprayed with a locating agent (Ninhydrin) so that they can become visible and be compared to other pure samples of the monomer.

Carbohydrates:

Carbohydrates are polymers made up of small sugar molecules joined together e.g. starch.

Carbohydrates contain Carbon, Hydrogen and Oxygen.

General Formula:  C_nC(H₂O)_n

Simplest Carbohydrate   C₆H₁₂O₆ (Glucose)

Glucose polymerise each other to form starch

Equation:

C₆H₁₂O₆   (C₅H₁₀O₅)_n +  nH₂O

Hydrolysic of Carbohydrates to convert them to simple sugar:

Starch can be broken down to glucose (Simple Sugar molecules by heating with Sulphuric Acid (Hydrolysis) – H₂O molecule is added.

Chromatography can be used to identify small molecules of sugar

Fats:

Fats are formed through condensation reaction of fatty acids (Carboxylic Acids) and Glycerol (3 Carboon atom chains having OH attached with every Carbon atom).

H₂O is also a by – product.

Fat is formed as a single large molecule so no need to write continuation brackets.

Glycserol contains three – OH functional groups per molecule and is hence known as a triol.

Each molecule of glycerol will combine with three molecules of fatty acids and form one molecule of fat.

Fats have same esteric linkages as Terylene (also known as polyster).

Fats can also be broken down to sodium salts of fatty acids and glycerol by boiling it with Acid or Alkalis (Hydrolysis).

Carboxylic Acids

Carboxylic Acids:

Carboxylic Acids are homogenous Series/ organic compounds containing the (CO₂H) group.

General Formula:   C_nH_{2n + 1} COOH

Functional Group:

Carboxylic Acids are not HydroCarbons, as they contain Oxygen in their Compounds. Hydro Carbonds are those organic compounds containing only Hydrogen and Carbon.

Properties Of Carboxyic Acids:

• All of them are 100% soluble in water.
• Chemical reaction of Carboxylic Acids are dependent upon C = O (Carboxyl) and H = O (Hydroxyl).
• They are weak acids (partially ionizes in water).

i.e. weaker than inorganic acids – inorganic compounds completely ionize hence more reactive than carboxylic acids.

In Organic Acid:

Organic Acid:

• Carboxylic Acids are partially ionized, to give Hydrogen ions in H₂
• They dissacociate only partially in water to form hydrogen ions.

Reactions With Metals:

Carboxylic Acid  + MetalMetal Salt   + Hydrogen

Ethanoic Acid  + Metal Magnesium Ethanoate + H₂

2CH₃COOH  + M_g  (CH₃COO)₂M_g   +  H₂

2HCOOH  + Ca (HCOO)₂Ca   +  H₂

Reactions With Carbonates + Bi Carbonates:

Carboxylic Acid  + Metal Carbonates Salt   +  CO₂   + H₂O

2CH₃COOH  +   Na₂CO₃2CHCOONa   +   CO₂   + H₂O

HCOOH    +     Na₂CO₃  HCOONa    +    CO₂   + H₂O

Reactions With Basis:

Carboxylic Acid  + Base  Salt   + H₂O

2CH₃COOH   + C₄O  (CH₃COO)₂C₄       + H₂O

HCOOH   +  C₃OHHCOOCs     +  H₂O

Production Of  Ehtanoic Acid (Carboxylic Acid):

Ethanoic Acid is dropped by the oxidation of Ethanol.

• Using Atmospheric Oxygen:
• By the oxidation of Ethanol in fermented solution with atmospheric oxygen in the presence of certain bacteria.
• When ethanol is left standing in air, bacteria bring about its oxidation to Ethanoic acid – acid fermentation.
• Acid fermentation is used to make vinegar (a dilute solution of Ethanoic acid.) The vinegar is produced from foods such as apples, rice and honey which are first fermented to give ethanol.

C₂H₅OH_(l)  +  O_2(g)             CH₃COOH_(l)  + H₂O_(l)

• Using Oxidizing Agents:
• By heating Ethanol with an oxidizing agent such ad acidified Potassium Dichromate(VI)  (K₂Cr₂o₇).
• Ethanol is oxidized much faster by warming the oxidizing agent K₂Cr₂o₇ in the presence of an acid.
• K₂Cr₂o₇ produces atomic Oxygen which more reactive than normal Oxygen (O).
• The Orange K₂Cr₂o₇ solution changes its colour to Green.

• H₂O is also produced as a byproduct while producing ethanol.

Esterification:

Esters are organic compounds formed by the combination of Carboxylic Acis with an Alcohol.

Catalyst – Concentrated Sulphuric Acid (H₂SO₄)

This Reaction is reversible.

H₂0 is produced as a by – product.

Ester is a sweet smelling organic  compound.

Preperation of Ester is known as esterification.

We can add Sodium Hydroxide (NaOH) and heat mixture to obtain Carboxylic acid and alcohol from ester – This is Hydrolysis.

          OH – from acid        H from alcohol    – Ester formation

The two functional groups react with each other. The C of the Carboxyl group bonds to the O of the OH group. The COO group where they join is called ester linkage.

The two molecules have joined by getting rid of a small  molecule, water. This is called condensation reaction.

In Condensation reaction, two molecules join together to form a large molecule, with the loss of a small molecule.

Uses of Esters:

• As a flavouring agent in foods.
• Used in cosmetics.
• Used as a solvent, to dissolve organic compounds that are insoluble in wate. They are volatile, hence they evaporate easily. (painting, ink, glues and nail polish).
• Esters are used in creating vegetable oils.

Alcohols

Alcohols:

Alcohols are a series of compounds with a hydroxyl group (-OH) joined to a carbon atom in a hydrocarbon chain.

General Formula: ( C_n H_{2n + 1}  OH)

Functional Group: (OH)

Note: The above mentioned Alcohols are all in Liquid state at room temperature as their boiling > room temperature. Also moving down the group, the mass and boiling points of Alcohols increases. Alcohols and Carboxylic Acids are not HydroCarbons as they  contain Oxygen atoms in their compounds.

Physical Properties:

• Alcohols are soluble in water(H₂O).
• Alcohols have OH in them but they are not Alkalies.
• Alcohols are more reactive than Alkanes and Alkenes, as they have more electronic density, and presence of hydroxyl (-O-H) and carboxyl group (-C-O) as shown below.

H₃C  –  CH₃       – Ethane

H₂C  –  CH_c      – Ethene

H₃C  –  CH₂ – O – H

Combustion:

Alcohol requires less Oxygen for combustion, as Oxygen is a part of it.

Complete Combustion:

Alcohol + O₂ CO + H₂O

C₂H₅OH + 3O₂ 2CO₂ + 3H₂0

Incomplete Combustion:

Alcohol + O₂  CO + Carbon Soot

This reaction, is highly exothermic, thus alcohols are used as fuels.

Oxidation:

Oxidation is gain of Oxygen and loss of Hydrogen.

Alcohols upon oxidation will form Carboxylic Acids + H₂O

In the presence of acidified Potassium Dichromate (H₂SO₄ K₂Cr₂O₇) an oxidizing agent.

C₂H₅OH     OH   + 2(O)CH₃OOH        H₂O

Hence:

Ethanol will become Ethanoic Acid and Propanol will become Propanoic Acid.

In this oxidation process, we can use either:

• Atmospheric Oxygen
• Acidified Potssium Dichromate , which changes its colour from Orange to Green.
• Purple acidified Potassium Magaate (VII) which is decolourised(K₂Cr₂O₇ MNO₄)

Preperation Of Alcohol:

There are two methods to obtain alcohol:

• Hydration Of Alkene (Lab Method)
• Fermentation (Industrial Method)

Hydration of Alkene  (Lab Method):

In this method, steam is added to Alkene, to convert it to Alcohol.

Conditions:

• Catalyst – Phosphoric Acid (H₃PO₄)
• Temperature – 300 °C

Hydration of Alkene, is actually adding water (H₂O) across the two double bonds Carbon of Alkenes

Fermentation (Industrial Method):

Fermentation is a process whereby an enzyme is used to break down glucose in sugar or starch into ethanol and CO₂ gas.

Fermentation is catalysed by the enzymes present in yeast.

Conditions:

• Temperature – 37°C (25 – 40°C)
• Temperature too high would destroy the yeast and temperature too low would result in yeast becoming dormant.
• Catalyst/ Biological Catalyst – Yeast (enzyme)
• No Oxygen should enter the setup. As Oxygen can react with Alcohol to convert it into Carboxylic Acid.
• CO₂ test (limewater turns milky ) to check the alcohol preparation.
• Alcohol can be separated after the process is completed, through fractional distillation, by using their respective boiling point.

Uses Of Alcohol:

There are different uses of Alcohols such as:

• Alcohol can be used as a constituent of alcohol beverages.
• As a solvent for detergents, perfumes and in medicines.
• As a fuel.