Chemistry in Everyday Life

Chemotherapy
Chemotherapy is the use of chemicals or drugs to selectively destroy infectious micro-organisms without destroying the live tissues or the host. Paul Ehrlich called drugs as magic bullets and the first milestone of his research was the discovery ofSalvarsan for curing syphilis, in 1909. In 1935, Gerhard Domagk, administered a dose of a dye called prontosil (inhibits the growth of streptococci bacteria) to cure his daughter's fever. This laid the foundation for modem chemotherapy and got a Nobel Prize for medicine for Domagk in 1939. Ernest Fourneal4 a French scientistin··J9J6 proved that in the human body, prontosil breaks down to give sulphanilamide. Sulphanilamide is the actual active agent that inhibits streptococci. This study led to the discovery of sulpha drugs and from there on growth of chemotherapy has reached amazing heights.
Analgesics
Drugs that are used as pain relieveFs are called analgesics. They are of two types:
(a) Narcotics
(b) Non-narcotics
Narcotics
These analgesics are mainly opium and its products. Some examples are
- morphine
- codeine and
- heroin
They are effective analgesics. but cause addiction. Over dosage can cause sleep and unconsciousness.
Non-narcotics
Drugs belonging to this group also have antipyretic properties (decrease body temperature). Aspirin and analgin are common drugs in this category.
Tranquillisers
Tranquillisers reduce anxiety and tension. They are of two types:
(1) Sedatives
(2) Antidepressants (mood elevators or Pep pills)
Sedatives
Sedatives are used for mentally agitated or violent patients. Equanil (chemical name - meprobanate) and calmpose (diazepam) are a couple of common drugs in this category.
Antidepressants or Mood Elevators or Pep Pills
Antidepressants are useful for patients who are highly depressed or have lost selfconfidence. These drugs produce a feeling of well-being and improve efficiency. Tofranil, vitalin, amphetamines and cocaine are some examples.
Antiseptics and Disinfectants
Sterilization is the process of complete elimination of micro-organisms. The chemicals used for sterilization are classified as:
(a) Antiseptics
(b) Disinfectants
Antiseptics
Antiseptic can be used to kill bacteria or prevent their multiplication. Antiseptics do not harm the living tissues. Therefore, they can be applied on cuts and wounds. Dettol, cetavelon, savlon, acriflavin, gentian-violet, mercuro chrome, boric acid and potassium permanganate are some examples.
Disinfectants
Disinfectants are used to kill bacteria. They are used to sterilize instruments, utensils, clothes, floors, sanitary fittings, sputum and excreta. They harm the living tissues and cannot be used on skin. Some examples are phenol, methyl phenol, hydrogen peroxide and sulphur dioxide.
Sometimes the same substance may be used as an antiseptic or disinfectant. When the concentration is less, it is an antiseptic and when the concentration is more, the substance acts as disinfectant. For instance, 0.2% solution of phenol is an antiseptic and 1.0% solution of phenol is a disinfectant.
Anti-fertility Drugs
With global population growing by the day, birth control has become essential. There are drugs that control ovulation and if regularly consumed, function as effective contraceptives. Some examples of birth control pills are orthonovum and Enovid. Orthonovum is a mixture of norethindrone and mestranol, estratriene. Envoid is a mixture of norethynodrel and mestranol.
Antacids
Tension and mental stress escalate the level of acid in bile juice. This hyperacidity can be combated using bases like calcium carbonate, magnesium hydroxide or aluminium hydroxide in the form of tablets or aqueous suspensions. These react with hydrochloric acid in the stomach and neutralize it partially. Gelusil and Digene are two examples of antacids
Antihistamines
Histamine is naturally present in almost all body tissues. When the human body meets substances causing allergies, histamine is released. For e.g., when a person is suffering from hay fever, histamine is released. Amines that are used as drugs to control the allergy caused by histamines are called Antihistamines. Histamine release induces allergic responses in the human body like:
(i) Tissue inflammation
(ii) Itching
(iii) Asthma
(iv) Skin irritation
Antibiotics
They are produced by micro-organisms that are toxic to other micro organisms. Alexander Fleming in 1920 found that bacteria donot flourish in nutrient agar surrounded by the fungus Penicillium notatum westling. He found that this fungus produces an antibiotic called penicillin. There are many varieties of pencillin with the empirical formula C9H11O4SN2R. Penicillin is very effective for:
(i) Pneumonia
(ii) Bronchitis
(iii) Sore throat
Six natural penicillins are isolated till now. They are got by substituting various groups for R.
Streptomycin
Streptomycin is very effective against tuberculosis, throat and lung infections, ear and kidney infections as well.
Tetracyclines
Tetracyclines (Chloro and oxy) are broad spectrum antibiotics (antibiotics capable of curing many infections) and cure diseases caused by many bacteria, large viruses, protozoa, parasites and rickettsiae. These can be orally administered since they are absorbed from the gastro intestinal tract.
Dyes - Chromophores
Unsaturated groups or groups with multiple bonds that impart color to the organic compound are called chromophores. Examples are the nitro, the nitroso and the azo groups
Chromogens
The compounds containing the chromophoric group are called the chromogens. Depth of their color increases with the number of chromophores.
Auxochromes as Dyes
Auxochromes (salt forming groups like hydroxyl, amino) do not impart color to the chromo gens in the absence of chromophores. However, when the chromogen has a chormophore, the auxochrome deepens the color of the chromogen. It is also used to make the chromogen a dye.
Dyes were obtained from animal and vegetable sources in the earlier days. Today most of the available dyes are prepared synthetically from aromatic compounds.
Classification of Dyes Based on Application
Direct or Substantive Dyes
These can be directly applied by immersing the cloth in a hot solution of the dye in water. They can be again classified into acid and basic dyes.
Acid dyes are sodium salts of sulphonic acid and nitrophenols. They are used for dyeing animal fibers (wool and silk) but not vegetable fibers (cotton). The dye solution is acidified with sulphuric or acetic acid.
Basic ,dyes are salts of color bases with hydrochloric acid or zinc chloride. They can directly dye animal fibers. They need a fixing agent called mordant (tannin) to dye vegetable fibers. These are used for dyeing silk and cotton.
Mordant or Adjective Dyes
Mordant is any substance that can be fixed to fiber and later dyed on. Hydroxides or basic salts of chromium aluminium or iron are examples. Tannic acid is a suitable mordant for basic dyes. The fabric is first dipped into the solution of mordant and then in the dye solution. An insoluble colored complex called lake is obtained. It is insoluble and fast to washing.
Ingrain Dyes
They are produced in the fiber itself during dyeing. For example, a cloth is soaked in an alkaline solution of [] - naphthol and dipped in a diazonium salt solution. Azodye is produced on the fiber due to coupling.
Vat Dyes
These are water insoluble colored compounds. They can be reduced to colorless (leuco) compounds, that are soluble in alkali and are easily reoxidized to give the dye. These dyes dye both animal and vegetable fibers directly. Mostly they are used for cotton fibers. The cloth treated with alkali is oxidised by air which makes the dye return to the insoluble form.
Classification of Dyes Based on Chemical Structure
Nitro and Nitroso dyes
Oldest synthetic dyes do not have much commercial importance.
Triphenyl methane dyes
These have brilliant colors but fade with washing and on exposure to light. They are used for coloring paper and typewriter ribbons. By introducing - NH2, NR2, or - OH groups (anxochromes) into the triphenyl methane ring (chromogen) a colorless leuco compound is obtained. The leuco compound gives the tertiary alcohol called the color base (colorless benzenoid compound) on oxidation. This in presence of acid readily changes to the quinonoid dye due to salt formation. We observe reversible changes.
Azodyes
They have the same chromophore - N =N -, the azo group. They differ in auxochromes. Common auxochromes are - NH2, NR2 and -OH groups. Examples are aniline yellow, butter yellow, methyl orange, methyl red, resorcin yellow, congo red, chrysoidone, bismark brown.
Phthaleins are got by the condensation· of phenol with phthalic anhydride in the presence of dehydrating agent like concentrated sulphuric acid or anhydrous zinc chloride. Examples are phenolphthalein, fluorescein and eosin.
Natural Dyes (Alizarin and Indigo)
Dyes can also be classified as natural and synthetic dyes. Compounds extracted from plants are called natural dyes. These were used in olden days to color fabrics. Alizarin (red) and indigo (blue) are two examples. Synthetic dyes came into being to provide more varieties of colors.
Alizarin belongs to the anthraquinone class of dyes. Indigo belongs to the indigoid type of dyes.
Perfumes
Perfumes have pleasant smell due to the esters used in their synthesis.
Characteristics of a good perfume are:
Harmonious and lasting smell
- Stability
- Volatility
- Ability to affix in the cosmetic
Sources of Perfumes
Plant Sources
- Essential oils of
- Flowers
- Leaves
- Fruits
- Roots or wood
Animal Sources
- Musk
- Ambtrgris
Composition
OdoriferOlls components
These are essential oils or synthetic substances or both. Constitute 2 -10% of the perfume and impart a pleasant smell to the perfume. Blending many odoriferous components will give a harmonious fragrance.
Fixatives
These impart stability by fixing volatile odoriferous substances. Examples are civet, musk, vanillin and castor.
Solvent
Solvents dilute the odor causing substances. These solvents should be odorless, volatile, inert and harmless. Ethyl alcohol and water are examples. Components of essen.tial oils such as terpenoids like citronellol, nerol, geraniol are widely used in perfumes.
Pyrfumes are widely used in soaps, lotions, shampoos, deodorants etc.
Deodorants
Decrease or eliminate body odors due to perspiration. Bacterial growth and action on perspiration causes objectionable odors. This odor varies from one person to another and also according to the diet and activity in the same person .
Salts of aluminium, iron and zinc prevent perspiration by their astringent action. Many such salts also have antibacterial properties and therefore are widely used as deodorants.
Talcum Powder
All kinds of facial and body powders contain hydrated magnesium silicate (talc - 3 Mg 0.4 SiO2.H2O). These powders absorb perspiration and superficial skin oil. A good powder should
- spread evenly
- stay on
- have the right degree of opacity (covering power)
Composition of Talcum Powder
- Calcium carbonate, magnesium carbonate - Help absorbency
- Titanium dioxide, zinc oxide, magnesium dioxide - Impart opacity
- Talc, metallic soaps - slipping
- Magnesium and iinc stearates - imparts adhesive property
Talc - Particle Size
Right grade or part;icle size of talc is important. A coarse talc has poor adhesiveness and is abrasive.
The particle size of talc should be less than 74 microns for face powder. The powder becomes soft, flufry, light and transparent when the talc is of the right nature.
Talc can:
- repel water
- slide over with minimum friction because of the flat structure of its particles.
Role of Magnesium carbonate
It is about five times more powerful than falc in absorbing water. Hence it is often used.to enhance absorbency and lightness of powders.
Boric acid in Powders
Boric acid being a germicide and a buffering agent is often added to powders. However, it is not advisable to use powders containing boric acid for babies.
Micro Alloys
Micro alloyed steels are intermediate carbon steel alloys with 0.3 to 0.6% carbon content. They also include vanadium, columbium (niobium), titanium and so on. These micro alloys are tougher than higher alloys. Their enhanced strength is due to the precipitation hardening reaction where nitrides or carbonitrides are formed in steel. Therefore, nitrogen level control is a key factor.
Today we have second-generation and third generation micro alloys: These have 0.1 to 0.3% carbon and 0.15% carbon respectively. These second-generation and third generation micro alloys are tougher than the earlier micro alloy grades.
Applications
High performance micro alloys are used in automotive, agricultural, truck and heavy equipment components.
Chemical Preservatives
Chemicals added to food materials to prevent the growth of micro organisms or prevent spoilage and to increase their shelf life are called preservatives. Some examples are given below:
1. Sodium benzoate is used as a preservative for fruits, fruit juices, jams and squashes. 0.06% to 0.1% (concentration) of sodium benzoate is added. It is easily soluble in water and therefore readily mixes with the food product.
2. Potassium metabisulphite or sodium metasulphite can also be used as preservative for fruits like apples, lichies and raw mango preparations besides fruit juices. However, these chemicals cannot be used for preserving colored food materials as sulphur dioxide, one of their products, behaves as a bleaching agent with acids. Sulphur dioxide is a very good chemical to kill the harmful micro organisms in food.
3. Vinegar (acetic acid) is usually used as a preservative in pickles.
Antioxidants
Antioxidants prevent rancidity in oils and fats. For example, butylated hydroxy anisole is a very common antioxidant. Vitamin-E is a natural antioxidant.
Artificial Sweetening Agents
For diabetic patients, sugar cannot be used as a sweetening agent. Artificial sweetening agents that are non-nutritive in nature are used as substituents for sugar (specially in soft drinks). Examples are saccharin (500 times sweeter than sucrose) and cyclamates.
However cyclamates are suspected to cause cancer and are banned generally. Aspartame (160 times sweeter than sucrose), another artificial sweetener is the methyl ester of the dipeptide aspartyl phenylalanine.
Edible Colors and Flavors
Food colors are used in ice creams, dairy products, sweet meat, soft drinks, confectionery, etc. These colors are also used in oral medicines like capsules, tablets, syrups and liquids to improve their appearance. Some of the primary colors are water soluble. They are: quinoline yellow, tartrazine, sunset yellow FCF, erythrosine, poncean 4R, carmoisine, amaranth and brilliant blue. Flavors are used to give pleasant smell for juices, jams etc. Vanillin is used as a flavor. Generally esters are used as flavors
Soaps and Detergents
Soaps are sodium or potassium salts of higher fatty acids like stearic, palmitic and oleic acids. Fatty acids are organic acids that have more than sixteen carbon atoms in their molecular structure. The sodium soaps are called hard soaps and the
potassium soaps are known as soft soaps. Soaps are obtained from oils and fats. For e.g., tristearin is got from beef and mutton tallow, tripalmitin from palm oil and triolein from lard (pig fat), olive oil and cotton seed oil. In India, soap is commonly got from coconut, groundnut, tit and mahua oils.
The Hot Process
Manufacture of soap by the hot process involves the following steps:
I. Saponification
Oil or fat is taken in a huge iron-pan called soap kettle and heated with open steam. 10% sodium hydroxide solution (lye) is added in a thin stream. The steam keeps the mass boiling and ensures thorough mixing as well. Saponification is complete after several hours to give a frothy mixture of sodium salts and glycerine.
Fat or Oil + Lye --------- Soap + Glycerol
II. Salting out of Soap
Saponfication is complete when we see a slight excess of the alkali in the transparent reaction mixture. Common salt or brine is then added to precipitate soap and heating is continued. Soap forms in the upper layer as a thick mass. This is known as salting out of soap.
The unused alkali solution in the lower layer is called spent lye or sweet lye. This along with glycerol and salts is drawn from below the reaction vessel. Glycerol can be recovered from this.
III. Finishing
The soap obtained after salting out is boiled again with sodium hydroxide for complete saponificaiton. This converts all the unsaponified fat. The spent lye is then drawn off; The solid soap is then boiled with water to dissolve excess of alkali. It is then allowed to settle when the impure soap called nigre forms the lower layer. The pure soap in the upper layer is transferred through a swing pipe to a steam-jacketed tank called crutcher.
It is then shredded into small chips, dried to the requisite amount of moisture content and mixed with colouring substances and perfumes. Some fillers like rosin, sodium silicate, borax and sodium carbonate are adde.d to laundry soaps. They have detergent value and are less expensive than soap.
In the next step, the soap is allowed to run into moulds and permitted to solidify. The bigger blocks are then cut with steel wires into smaller slabs, which are then cut into smaller cakes and stamped.
The Cold Process
Oil or molten fat is taken in an iron pan fitted with a stirrer. It is then treated with lye (any strong alkaline solution, like potassium hydroxide used for washing or cleansing). Stirring is continued till the soap begins to set. After solidification in frames, it is cut into slabs and further into cakes. All the glycerine remains in the soap. Starch or other fillers are thoroughly mixed with the oil before lye is added. This process is not so economical as the hot process and the soap obtained is also not pure.
Proportions of Ingredients
Alkali 1 part
Water 7 parts
Starch I part
Difference between Toilet Soap and Laundry Soap
Toilet Soap
Laundry Soap
High quality fats and oils as raw materials
Cheaper quality fats and oils
Expensive perfumes added
Cheap perfumes added
Care is taken to ensure that there is no free alkali content to prevent in juries to skin
No such care is taken
No fillers
Fillers present
Special Varieties of Soap
- Floating Soaps
Made by beating large quantities of air into soap in a crutcher when the soap is in a creamy state
- Transparent Soaps
Contains glycerol or alcohol. Obtained by dissolving soap in alcohol and evaporating the solvent alcohol.
- Medicated Soaps
Medicinal substances added. Examples are neem soap and carbolic soap.
- Shaving Soaps
Potassium sodium stearates (produces lasting lather) containing gum and glycerine to prevent lather drying.
Cleansing Action of Soap
Unimolecular film of soap molecules on water surface
A soap has two dissimilar ends. At one end is the hydrocarbon chain that is nonpolar and hydrophobic (oil soluble). At the other end there is the carboxylate ion that is polar and hydrophilic (water soluble).
When soap is added to water, its molecules make a unimolecular film on the surface of water with their carboxyl groups dissolved in water and the hydrocarbon chains standing on end to form a hydrocarbon layer
Cleansing action of a soap
When a soiled cloth is soaked in soap solution, soap dissolves dirt (fat or oil with dust absorbed in it) by micelle formation. Micelles are an aggregate of molecules in a colloidal solution. The oil or fat is at the centre of the sphere with fat-soluble hydrocarbon chains of soap dissolved in it. The water soluble carboxylate ions make a hydrophilic surface around this sphere and render the miscelles of oil or fat water-soluble. Thus the micelles are dissolved in water and are washed away. Soap tynds to concentrate on the solution surface and therefore lowers its surface tension, causing foaming. This helps it to penetrate the fabric. It emulsifies fat in dirt to form micelles and renders all the micelles water-soluble. Thus the water washes the dirt away.
Synthetic Detergents
They possess the desirable properties of ordinary soaps and can be used with hard water and in acidic solutions as well. Synthetic detergents are sodium salts of long chain benzene sulphonic acids or sodium salt of long chain alkyl hydrogen sulphates. Their calcium or magnesium salts are soluble in water.
The hydrophobic part is the hydrocarbon chain and the water soluble part can be:
- An anionic group like sulphate or sulphonate
- A cationic group like amine salt or quaternary ammonium compound
- A non-ionic group like alcohol or ether
Some examples of detergents are as follows:
Alkyl Sulphates (Anionic)
- CH3(CH2)10CH2OSO3Na+- sodium lauryl sulphate
- CH3(CH2)16CH2OSO3Na +- sodium stearyl sulphate
- Alkyl benzene sulphonates (Anionic)
Properties
Some of the synthetic detergents with a branched hydrocarbon chain have very low biodegradability. They are resistant to bacterial attack and are not fully degraded in sewage treatment units. Therefore, they cause water pollution when they are discharged into a river or any other water body. Phosphate salts present in synthetic detergents cause rapid growth of algae that deplete the oxygen content in the water. (A condition known as eutrophication). Due to this aquatic animals die resulting in the imbalance of the ecosystem as well. Tbese detergents lower tbe surface tension of water and act as cleansing agents (wetting agents). They can be used for delicate fabrics because they do not hydrolyze to give hydroxyl ions. They have equal action in both hard and soft water.
Composition of a Common Detergent
Sodium alklbenzene sulphonate
18%
Dedusting agent
3%
Foam booster
3%
Sodium tripolyphosphate, builder
50%
Anti-corrosion agent
6%
Optical brightener
0.3%
Water and inorganic filler
19.7%
Tripolyphosphate can produce hydroxyl ions by reacting with water. It keeps the wash water slightle alkaline, to emulsify grease particles. They can also tie up calcium and magnesium and magnesium ions that cause hardness of water.
Advantages of Detergents Over Soaps
Soaps are nor suitable when hard water is used. Detergents can be used with both hard and soft water. Detergents are more soluble in water than soaps. They also have a stronger cleansing action than soaps. Detergents do not need expensive vegetable oil for their preparation as they can be prepared form hydrocarbons of petroleum. They can be used in acidic solution whereas soaps cannot be used (free fatty acids are precipitated).
Soaps
Detergents
Soaps are sodium salts of higher fatty acids
Detergents are sodium salts of long chain benzene sulphonic acid or the sodium salts of a long chain alkyl hydrogen sulphate
Calcium and magnesium salts of soaps are in soluble in water. Therefore cleansing action of soap reduces in hard water
Calcium and magnesium salts of detergents are soluble in water. Therefore cleansiing action of detergents remain unaffected in hard water
Soaps are prepared form natural oils and fats
Synthetic detergents are prepared form hydrocarbons of petroleum
Soaps cannot be used in acidic medium
Detergents can be used in acidic medium
Soaps are biodegradable
Most of the detergents are non-biodegradable