Chemistry in Everyday Life

CHEMISTRY IN EVERYDAY LIFE

Drugs : - Drugs are chemicals of low molecular masses, interact with macromolecular targets and produce a biological response. response. Medicines : - Drugs which have therapeutic biological response response and used in diagnosis diagnosis , prevention and treatment of diseases; are called call ed medicines. i.e. All medicines are drug, but all drugs are not medicine.

Chemotherapy :- The treatment of disease by means of chemicals that have specific toxic effect upon the disease producing micro-organisms or that selectively destroy neoplastic tissues is called chemotherapy. Classification of drugs : -Drugs are classified on the basis of (1) pharmacological effect O (2) drug action H2N S NH R (3) molecular targets Sulphonamide O (4) chemical structure

Interaction of drugs with targets Targets- Macromolecules of biologcal origin such as Proteins, carbohydrates, nucleic acids and lipids l ipids Enzymes - Proteins which perform the role of biolgical catalysts in the body Receptors- Proteins which are responsible for the communication system in the body . Communication system in the body Following steps are involved for the communication system in the body :(1) Receptor at its binding site receive chemical messenger. (2) Shape of the receptor changed after attachment of messenger. (3) After transfer of message to the cells,the messenger leaves the site of receptor, and receptor regains its structure. Receptors as drug targets (a) Drugs ( as antagonists) bind to the active site of receptor and inhibit its natural functioning. These are useful when blocking of the message is required. (b) Drugs ( as agonists) mimic the natural messenger by switching on on the receptor. These are useful when there is lack lac k of natural chemical messenger. Enzymes as drug targets Drugs hinder the formation formation of enzyme-substrate enzyme-substrate complex i.e. inhibit inhibit the catalytic activity of the enzyme.. It can be done in two ways :(a) Drugs [ as competitive inhibitor] block the active site of enzyme for the sustrate. (b) Drugs [ as binding inhibitor] bind in the allosteric site of the enzyme and change the shape of the active site in such a way that substrate can not recognise it. H3C H2N OH

Cl

SO 2NH2

[ Sulphanilamide ] CO

CH3 H3C HO

SO2

O

H3C

CH3 Cl

[ Chloroxylenol ]

[ Saccharin ] Ortho-sulphobenzimide

O

Cl

S

[ Terpineol ]

NH

HO

OH

C

Cl

[ Bithionol ]

Cl

CH3

[ Aspirin ] 2-acetoxybenzoic acid COOH

Medicines

Examples

Role

Analgesics Aspirin (2-acetoxybenoic acid ), ( Non-narcotic ) Analgin, Seridon, Anacine, Aspro.

Drugs used for relieving pain

Analgesics (Narcotic )

Opium, Heroin , Pethidine , Codeine, Morphine

Antimicrobials

Chlorine, Formaldehyde, Phenol, Ozone

Antibiotics

Penicillin, Streptomycin, chloramphenicol

Antiseptics

Dettol, Bithional,Tincture iodine, The chemical sustances which prevent the growth Methyl blue, Salicylic acid, 0.2% of micro-organism or kill them but are not harmful phenol, picric acid, Resorcinol to the living human tissues. 1% phenol, chlorine (Cl2) , A substance that kills micro-organisms, but is not safe for contact with living tissues. It is Sulphurdioxide ( SO 2) used for toilets, instruments.

Disinfectants

Antacids Antihistamines

,  Al(OH) 3 gel , ,  AlPO 4 Mg(OH) 2

NaHCO

3

MgCO

They reduce tension and pain. They produce sleep and unconsciouness. The substance which kills or destroys micro-organism The chemical substances produced by micro organism (bacteria,fungi,molds ) that can inhibit the growth or even destroy other micro-organism.

3

Brompheniramine ( Dimetapp) Terfenadine ( Seldane)

,

The chemical substances which can reduce or neutralise the acidity. It is used to treat allergy

Tranquilizers

Valium, Serotonin and It reduce the mental anxiety by acting on higher Barbiturates i.e derivative of centres in the central nervous system. barbituric acid such as Veronal, Equanil,Amytal,nembutal.luminal and seconal

Antipyretics

Aspirin, Paracetamol, Analgin, Phenacetin.

It is used to bring down the temperature of human body.

Anaesthetics

Cyclopropane,nitrous oxide, xylocain

These drugs produce loss of sensation.

Hypnotics

Luminal, seconal, soaryl

It produce sleep and are habit forming

Sedatives

Valium, Barbiturates

They act as depressant and suppress the activities of central nervous system.

Sulpha drug

Sulphanilamide, Sulphadiazine, Sulphaguanidine

It can be used inplace of antibiotics. They inhibit the growth of micro-organisms.

Antifertility drugs

Norethindrone, Ethynylestradiol ( novestrol )

These are the steroids used to control the pregnancy

Penicillin was the first antibiotic discovered by Alexander Fleming from the mould penicillium notatum Phenol act as antiseptic ( 0.2% phenol) and as disinfectant ( 1% phenol) Bithionol/Bithional is added to soap to impart antiseptic properties. Dettol is a mixture of chloroxylenol and terpeneol. Pathogon is an organism that causes disease. Bactericidal antibiotics:- These drugs kill the organisms in the body ( Penicillin, Ofloxacin,Aminoglycosiders) Bacteriostatic antibiotics:- These drugs inhibit the growth of organism(Tetracycline, Chloramphenicol,Erythromycin)

Spectrum of an antibiotics:- The

full range of micro-organism attacked by an antibiotic is called its spectrum. The antibiotics which are effective aganist several different types of micro-organism are called broad spectrum antibiotics ( Tetracycline, Chloramphenicol,Ofloxacin, Vancomycin) The antibiotics which are effective only aganist certain specific group of micro-organisms are called narrow spectrum antibiotics ( Penicillin)

Artificial sweetening agent s: Saccharin - ( ortho-sulphobenzamide) 550 times as sweet as cane sugar.It is excreted from the body in urine unchanged. It appears to be entirely inert and harmless when taken. Aspartame- ( methyl ester of dipeptide formed from aspartic acid and phenylalanine) 100 times as sweet as cane sugar. It is limited to cold foods and soft drinks because it is unstable at cooking temperature. Alitame - 2000 times as sweet as cane sugar. It is stable but it is difficult to control its sweetness. Sucrolose - ( trichloro derivative of sucrose) 600 times as sweet as cane sugar. It is stable at cooking temperature and does not provide calories.

Food preservatives They prevent spoilage of food due to microbial growth. e.g.- Sodiumbenzoate, salts of propanic acid and sorbic acid. Sodium benzoate ( C6H5COONa ) is metabolised by conversion to hippuric acid ( C6H5CONHCH 2COOH ) which is ultimately excreted in the urine.

Saponification

Base hydrolysis of ester is known as saponification

H 2C

O

COC 17H35

HC

O

COC 17H35

H 2C

O

COC 17H35

+



3 NaOH

3 C 17H35COONa

+

H 2C

OH

HC

OH

H 2C OH [ Sodium stearate ] [ soap ] Glycerol ( Glycerine )

[ Glyceryl ester of stearicacid ( fat) ]

Soaps are sodium or potassium salts of stearic, Oleic or palmitic acid The soap obtained by saponification remains in colloidal form and is precipitated from the solution by adding sodium chloride. Potassium soaps are soft to the skin than sodium soap. Toilet soaps are prepared by using better grade fats and oils a nd care is taken to remove excess alkali. Soaps that float in water are made by beating tiny air bubbles before their hardening Transparent soaps are made by dissolving the soap in ethanol and then evaporating the excess solvent. Shaving soaps contain glycerol to prevent rapid drying and rosin ( forms sodium rosinate ) to produce lathers Laundry soaps contain fillers like sodium rosinate, sodium silicate, borax and sodium carbonate.

Synthetic detergents These are salts of long chain sulphonates and sulphates. They are two types:[1] Sodium salts of long chain benzenesulphuric acid H3C

( CH2 )11

Dodecylbenzene

H2SO 4

H3C

( CH2) 11

NaOH (aq)

SO3 H

H3C

+



( CH2) 11

SO3Na

Sodium dodecylbenzenesulphonate

Dodecylbenzenesulphonic acid

[2] Sodium salts of long chain alkyl hydrogen sulphate CH 3(CH2)10CH 2OH

Lauryl alcohol

H2SO 4

CH 3(CH2)10CH 2OSO 3H

NaOH (aq)

Lauryl hydrogensulphate



+

CH 3(CH2)10CH 2OSO 3 Na

Sodium laurylsulphate

On the basis of charge on the polar head, detergents are classified as :(a) Anionic detergents:- The polar head is negatively charged, e.g. Sodium laurylsulphate and + CH3 Sodium dodecylbenzenesulphonate (b) Cationic detergents:- The polar head is positively charged. H C (CH ) N CH3 Br 3 2 15 e.g. Acetates , chlorides or bromides of quaternary amines.



CH

3 (c) Non-ionic detergents:Cetyltrimethyl ammonium bromide Polar head is neutral. These are esters of high molecular mass, formed by reaction between polyethylene glycol and stearic acid. H O

CH 3(CH 2)16COOH

+

HO(CH 2CH 2O)nCH 2CH 2OH



2

CH 3(CH 2)16COO(CH 2CH 2O)nCH 2CH 2OH

Polyethyleneglycol Stearic acid Explain the following term as used in medicinal chemistry Target molecules or drug targets. (i) A knowledge of the physiological function of the drug target in the body helps us to choose a compound which can interact with the target and hence is expected to be therapeutically active. These compounds are called lead compounds and drugs are designed from these compounds (ii) Drugs interact with macromolecules like proteins, carbohydrate, lipids and nucleic acids and hence these are called drug targets .Proteins perform several roles in the body. Proteins which act as biological catalysts are called enzymes, those which are involved in communication system are called receptors Carrier proteins carry polar molecules across the cell membrane Nucleic acids have coded genetic information in the cell and, lipids and carbohydrates form structural. part of cell membranes Why the medicines should not be taken without consulting the doctors? Side effects are caused when a drug binds to more than one receptor site. Therefore, a doctor must be consulted to choose the right drug which has the maximum affinity for a particular receptor site to have the desired effect. Further, dose of the drug is also crucial because some drugs like opiates in higher doses act as poisons and may cause death. Which forces are involved in holding the drugs to the active site of enzymes? Ans. Hydrogen bonding, ionic bonding, dipole-dipole interactions or van der Waals interactions. Amino acids serine, aspartic acid and phenylalanine are present on the active site of an enzyme. Structures of these amino acids are given in the book. Explain which forces may be involved in binding the drug to the enzyme if the drug inhibits the holding of substrate on the active site of enzyme. -OH group of serine, -COOH group of aspartic acid and phenyl ring of phenylalanine help to bind the drug to the enzyme. Why do drugs designed to cure some ailment in one organ in the body not affect the other parts? Example with an example. OR Antacids and antiallergic drugs interfere with the function of histamines but why do these not interfere with the function of each other? Drugs designed to cure some ailment in one organ in the body do not affect the other because they work on different receptors. For example, secretion of histamine causes allergy. It also causes acidity due to release of hydrochloric acid in the stomach. Since antiallergic and antacids drugs work on different receptors, therefore, antihistamines remove allergy while antacids remove acidity .Low level of noradrenaline is the cause of depression. What type of drugs are needed to cure this problem ? Name two drugs. In event of low level of neurotransmitter, noradrenaline, antidepressant drugs are required. These drugs inhibit the enzymes which catalyse the degradation of noradrenaline. If the enzyme is inhibited,noradrenaline is slowly metabolized and hence activates its receptor for longer periods of time thereby reducing depression. Two important drugs are iproniazid and pheneizine.

Why are cimetidine and ranitidine better antacids than sodium hydrogen carbonate or magnesium or aluminum hydroxide If excess of NaHCO3or Mg(OH)2 or Al(OH)3 is used, it makes the stomach alkaline and thus triggers the release of even more HCl which may cause ulcers in the stomach. In contrast, cimetidine and ranitidine prevent the interaction of histamine with the receptor cells in the stomach wall and thus release lesser amount of HCl. What is tincture of iodine ? What is its use ? 2-3% solution of iodine in alcohol and water is called tincture of iodine. It is a powerful antiseptic. It is applied to wound. Why detergents are called soap less soap? Detergents are cleansing agents which have all the properties of a soap but do not contain any soap. How are detergents better than soaps? They can be used in hard water as well in acidic solution. The reason being that sulphonic acids and their calcium and magnesium salts are soluble in water but the fatty acids and their calcium and magnesium salts are insoluble. ' Why do we need to classify drugs in different ways? Drugs have been classified in different ways depending upon their pharmacological effect, upon their action on a particular biochemical process, on the basis of their chemical structure and on the basis of molecular targets. Each classification has its own usefulness. Classification on the basis of pharmacological effect is useful for doctors because it provides them the whole range of drugs available for the treatment of a particular disease. Classification on the basis of action on a particular biochemical process is useful for choosing the correct lead compound for designing the synthesis of a desired drug. Classification on the basic of chemical structure helps us to design the synthesis of a number of structurally similar compounds having different substituents and then choosing the drug having least toxicity. Classification on the basis of molecular targets is useful for medicinal chemists so that they can design a drug are most effective for a particular receptor site. Why do soaps do not work in hard water? Hard water contains calcium and magnesium salts. Therefore, in hard water soaps get precipitated as calcium and magnesium soaps which being insoluble stick to the clothes as gummy mass. Can you use soaps and synthetic detergents to check the hardness of water? Ans. Soaps get precipitated as insoluble calcium and magnesium soaps in hard water but detergents do not. Therefore, soaps but not synthetic detergents can be used to check the hardness of water . What are biodegradable and non-biodegrable detergents. Give one example of each. Detergents having straight hydrocarbon chains are easily degraded or decomposed by microorganisms and hence are called biodegradable detergents while detergents containing branched hydrocarbon chains are not easily degraded by the microorganisms and hence are called non-biodegradable detergents. Consequently, non-biodegradable detergents accumulate in rivers and waterways thereby causing severe water pollution. Examples of biodegradable detergents are sodium lauryl sulphate, sodium 4-(1-dodecyl)benzene sulphonate and sodium 4-(2- dodecyl)benzenesulphonate. An example of non-biodegradable detergent is sodium 4-(1, 3,5, 7-tetramethyloctyl)benzenesulphonate