Chemistry in Everyday Life Online Test 12th Science

Prof. Vladimir Prelog was a Swiss Chemist who shared 1975 Nobel Prize for Chemistry with John W Cornforth for his work on Stereo Chemistry.

Prof. Vladimir Prelog has done wide ranging research on alkaloids, antibiotics, enzymes and other natural compounds. He was distinguished for his contribution to the development of modern stereo chemistry. Prelog synthesized many natural products and worked on problems of stereo chemistry like adamenline, boromycin analoids and rifamycins.

The word drug is derived from the French word “drogue” meaning “dry herb”. A drug is a substance that is used to modify or explore physiological systems or pathological states for the benefit of the recipient.

A drug is used for the purpose of diagnosis, prevention, cure/relief of a disease. A drug which interacts with macromolecular targets such as proteins to produce a therapeutic and useful biological response is called medicine.

An ideal drug is the one which is non-toxic, bio-compatible and bio-degradable, and it should not have any side effects.

The specific treatment of a disease using medicine is known as chemotherapy. The drug which interacts with macromolecular targets such as proteins to produce a therapeutic and useful biological response is called medicine.

Generally, most of the drug molecules that are used now a days have the above properties at lower concentrations. However, at higher concentrations, they have side effects and become toxic.

The medicinal value of a drug is measured in terms of its therapeutic index. Higher the value of therapeutic index, safer is the drug.

Drugs are classified based on their properties such as chemical structure, pharmacological effect, target system, site of action, etc.

In this classification, drugs with a common chemical skeleton are classified into a single group. For example, ampicillin, amoxicillin, methicillin, etc. all have similar structure and are classified into a single group called penicillin.

Compounds having similar chemical structure are expected to have similar chemical properties. However, their biological actions are not always similar. For example, all drugs belonging to penicillin group have same biological action, while groups such as barbiturates, steroids etc. have different biological action.

Streptomycin inhibits the initiation of protein synthesis, while erythromycin prevents the incorporation of new amino acids to the protein.

If we want to block a message, a drug that binds to the receptor site should inhibit its natural function. Such drugs are called antagonists. In contrast, there are drugs which mimic the natural messenger by switching on the receptor. These types of drug are called agonists and are used when there is lack of chemical messenger.

To treat acidity, we have been using weak bases such as aluminium and magnesium hydroxides. But these can make the stomach alkaline and trigger the production of much acid.

Tranquilizers:

They are neurologically active drugs. Acts on the central nervous system by blocking the neurotransmitter dopamine in the brain. It is used in treatment of stress, anxiety, depression, sleep disorders and severe mental diseases like schizophrenia.

Minor tranquilizers: Diazepam (Valium), alprazolam

Major tranquilizers: Haloperidol, clozapine

Analgesics reduce the pain without causing impairment of consciousness. They alleviate pain by reducing local inflammatory responses.

Anti-inflammatory drugs:

Acetaminophen or paracetamol, Ibuprofen, Asprin.

Antipyretics:

Example Salicylates Acetylsalicylic acid (aspirin), Acetaminophen or Paracetamol

Uses of Analgesics:

• Used for short-term pain relief and for modest painlike headache, muscle strain, bruising, or arthritis
• These drugs have many other effects such as reducing fever (antipyretic) and preventing platelet coagulation. Due to this property, aspirin finds useful in the prevention of heart attacks
• Reduces fever by causing the hypothalamus to override a prostaglandin-induced increase in temperature.

Opioids (Narcotic Analgesics):

Examples: Morphine, codeine

Relive pain and produce sleep. These drugs are addictive. In poisonous dose, these produces coma and ultimately death.

Uses:

Used for either short-term or long-term relief of severe pain. Mainly used for post-operative pain, pain of terminal cancer.

Anaesthetics causes loss of sensation, in the area in which it is applied without losing consciousness. They block pain perception that is transmitted via peripheral nerve fibres to the brain. They are often used during minor surgical procedures.

Local anaesthetics:

Ester-linked local anaesthetic – Procaine

Amide-linked local anaesthetic – Lidocaine

General anaesthetics:

Intravenous general anaesthetics– Propofol

Inhalational general anaesthetics – Isoflurane

General anaesthetics: Cause a controlled and reversible loss of consciousness by affecting central nervous system

Uses: They are often used for major surgical procedures.

Antacids: Milk of Magnesia, Sodium bicarbonate, calcium bicarbonate, aluminium hydroxide Ranitidine, Cemitidine, Omeprazole, rabeprazole.

Antacids: Neutralize the acid in the stomach that causes acidity.

Uses: To relieve symptoms such as burning sensation in the chest/ throat area (heart burns) caused by acid reflux.

Antihistamines: Cetirizine, levocetirizine, desloratadine, brompheniramine Terfenadine

They Block histamine release from histamine-1 receptors.

Uses: To provide relief from the allergic effects

Beta-Lactams: Penicillin, ampicillin, cephalosporins, carbapenems, and monobactams

Inhibits bacterial cell wall biosynthesis

Used to treat skin infections, dental infections, ear infections, respiratory tract infections, pneumonia, urinary tract infections, and gonorrhoea

Macrolides: Erythromycin, azithromycin

Targets bacterial ribosomes and prevent protein production

Uses: To treat respiratory tract infections, genital, gastrointestinal tract and skin infections

Fluoroquinolones can be used to treat urinary tract infections, skin infections, and respiratory infections (such as sinusitis, pneumonia, bronchitis), pulmonary infections in cystic fibrosis.

Tetracyclines:

Examples: Doxycycline, minocycline, oxytetracycline

Inhibit the bacterial protein synthesis via interaction with the 30S subunit of the bacterial ribosome

Antiseptics Stop or slow down the growth of microorganisms – Applied to living tissue. Examples Hydrogen peroxide, povidone-iodine, benzalkonium chloride.

Disinfectants:

Examples: Chlorine compounds, alcohol, Hydrogen peroxide.

Stop or slow down the growth of microorganisms – Generally used on inanimate objects.

Advantages of food additives:

• Uses of preservatives reduce the product spoilage and extend the shelf-life of food
• Addition of vitamins and minerals reduces the mall nutrient
• Flavouring agents enhance the aroma of the food
• Antioxidants prevent the formation of potentially toxic oxidation products of lipids and other food constituents

Preservatives are capable of inhibiting, retarding or arresting the process of fermentation, acidification or other decomposition of food by growth of microorganisms. Organic acids such as benzoic acid, sorbic acid and their salts are potent inhibitors of a number of fungi, yeast and bacteria. Alkyl esters of hydroxy benzoic acid are very effective in less acidic conditions.

Acetic acid is used mainly as a preservative for the preparation of pickles and for preserved vegetables. Sodium meta-sulphite is used as preservatives for fresh vegetables and fruits.

In addition to chemical treatment, physical methods such as heat treatment (pasteurisation and sterilisations), cold treatment (chilling and freezing) drying (dehydration) and irradiation are used to preserve food.

Antioxidants are substances which retard the oxidative deteriorations of food. Food containing fats and oils is easily oxidised and turn rancid. To prevent the oxidation of the fats and oils, chemical BHT (butyl hydroxy toluene), BHA (Butylated hydroxy anisole) are added as food additives. They are generally called antioxidants.

Those compounds that are used like sugars (glucose, sucrose) for sweetening, but are metabolised without the influence of insulin are called sugar substituents. e.g. Sorbitol, Xylitol, Mannitol.

Synthetic compounds which imprint a sweet sensation and possess no or negligible nutritional value are called artificial sweeteners. Eg. Saccharin, Aspartame, sucralose, alitame etc…

Soaps and detergents are used as cleansing agents. Chemically soap is the sodium or potassium salt of higher fatty acids. Detergent is sodium salt of alkyl hydrogen sulphates or alkyl benzene sulphonic acids.

Soaps are made from animal fats or vegetable oils. They contain glyceryl esters of long chain fatty acids. When the glycerides are heated with a solution of sodium-hydroxide they become soap and glycerol.

The quality of a soap is described in terms of total fatty matter (TFM value). It is defined as the total amount of fatty matter that can be separated from a sample after splitting with mineral acids., Higher the TFM quantity in the soap better is its quality.

As per BIS standards, Grade-1 soaps should have 76% minimum TFM, while Grade-2 and 3 must have 70 and 60%, minimum respectively. The other quality parameters are lather, moisture content, mushiness, insoluble matter in alcohol etc.

The cleansing action of soap is directly related to the structure of carboxylate ions (palmitate ion) present in soap. The nonpolar portion is hydrophobic while the polar end is hydrophilic. The hydrophobic hydro carbon portion is soluble in oils and greases, but not in water. The hydrophilic carboxylate group is soluble in water.

Synthetic detergents are formulated products containing either sodium salts of alkyl hydrogen sulphates or sodium salts of long chain alkyl benzene sulphonic acids. There are three types of detergents.

The term Polymer is derived from the Greek word ‘polumeres’ meaning “having many parts”. The constitution of a polymer is described in terms of its structural units called monomers.

Polymers consists of large number of monomer units derived from simple molecules. For example: PVC (Poly Vinyl Chloride). is a polymer which is obtained from the monomer vinyl chloride. Polymers can be classified based on the source of availability, structure, molecular forces and the mode of synthesis.

The process of forming a very large, high molecular mass polymer from small structural units i.e., monomer is called polymerisation. Polymerisation occurs in the following two ways

• Addition polymerisation or chain growth polymerisation 
• Condensation polymerisation or step growth polymerisation

The addition polymerisation can follow any of the following three mechanisms depending upon the reactive intermediate involved in the process.

• Free radical polymerisation
• Cationic polymerisation
• Anionic polymerisation

Condensation polymers are formed by the reaction between functional groups an adjacent monomers with the elimination of simple molecules like H₂O, NH_3. Nylon – 6,6 can be prepared by mixing equimolar adipic acid and hexamethylene – diamine to form a nylon salt which on heating eliminate a water molecule to form amide bonds_.

Terylene (Dacron) is used in blending with cotton or wool fibres and as glass reinforcing materials in safety helmets.

In the year 1839, Charles Good year accidently dropped a mixture of natural rubber and sulphur onto a hot stove. He was surprised to find that the rubber had become strong and elastic. This discovery led to the process that Good year called vulcanization.

Examples of Biodegradable Polymer:

• Polyhydroxy butyrate (PHB)
• Polyhydroxy butyrate-co-A- hydroxyl valerate (PHBV)
• Polyglycolic acid (PGA), Polylactic acid (PLA)
• Poly (∈ caprolactone) (PCL)

The materials that are readily decomposed by microorganisms in the environment are called biodegradable. Natural polymers degrade on their own after certain period of time but the synthetic polymers do not. It leads to serious environmental pollution.

The free radical polymeristion of the monomer, 2-chloro buta-1,3-diene(chloroprene) gives neoprene. It is used in the manufacture of chemical containers, conveyer belts.

In all living systems, the biochemical reactions are catalysed by enzymes. Hence, these enzyme actions are highly essential for the normal functioning of the system. If their normal enzyme activity is inhibited, then the system will be affected. This principle is usually applied to kill many pathogens.