Analytical Chemistry

CSIR UGC NET (CHEMICAL SCIENCES) CSIR UGC COMBINED NATIONAL ELIGIBILITY TEST (CSIR UGC NET) for RESEARCH FELLOWSHIP & LECTURESHIP for chemical sciences is conducted twice every year (in June & in December) to select right candidates to award research fellowships, initially for two years (JRF) which can be further extended for three more years (SRF). This exam is also popularly known as CSIR NET or CSIR UGC NET exam. Most of the admissions into Ph.D courses in prestigious institutions of India like IISc, Central University of Hyderabad, IIT's and several CSIR laboratories require the qualification in CSIR UGC NET exam. CSIR NET EXAM PATTERN (NEW) According to new pattern implemented from June 2011 onwards, the CSIR NET exam in chemical sciences is: * a single paper test having multiple choice questions (MCQs) * carries a maximum of 200 marks. * is divided into three parts (A, B & C). * conducted for the duration of 3 hours. Part - A carries 20 questions and is common to all the subjects. The candidate is required to answer any 15 questions. Each correct answer is awarded with 2 marks. The total marks allocated to this section shall be 30 out of 200.

The revised pattern for this part will test general aptitude with emphasis on logical reasoning, graphical analysis, analytical and numerical ability, quantitative comparison, series formation, puzzles etc. There is no syllabus prescribed for this. Part - B contains 50 multiple choice questions generally covering the topics given in the syllabus. A candidate is required to answer any 35 questions and each correct answer is awarded with 2 marks. The total marks allocated to this section shall be 70 out of 200. The standards of these questions from this section may range from 10+2 to PG level in chemistry subject. Part - C consists of 75 questions. A candidate shall be required to answer any 25 questions, each carrying 4 marks. The maximum marks allocated to this section is 100 out of 200. The questions shall be of analytical nature where a candidate is expected to apply the scientific knowledge in chemistry to arrive at the solution to the given problem. There will be negative marking @25% for each wrong answer. P # a of r qu t est io

To M be ar att ks em all pte ot

M axi m u m

te d pe r ma ea ns d rk ch s q ue sti on A 2 15 2 30 0 B C

50 35 2 70 75 25 4

10 0

Cutoff marks for previous CSIR NET exams in chemical sciences paper are tabulated below. Note that these are percentages and are not same for each exam. Multiply with 2 to get actual score per 200. CSIR never announced the criteria for deciding the cutoff marks. They never announced them before exam too. So no guess work please. % Cutoff marks for Chemical sciences

Mon Junior Research Lectureship th & Fellowship (LS) Year (JRF) of SC/S General/ SC/S Exa General/ OBC OBC OBC T OBC T m DEC , 2011

45%

47% 35%

40%

40% 30%

JUN E, 2012

47%

47% 37%

42%

42% 32%

DEC , 2012

43.5%

43.5 33.5 % %

38.5%

38.5 28.5 % %

JUN E, 2013

53%*

53% 43% * *

48%*

48%*

DEC , 2013

55%

55% 45%

50%

50% 40%

50%

50% 40%

45%

45% 35%

JUN E,

38% *

1. Chemical periodicity

2014 Dec, 2014

52%

46.80 41.60 46.80% % %

42.1 37.44 2% %

* These were not announced by CSIR officially. I got them from various sources. I cannot guarantee the validity of above data. Please confirm with CSIR before coming to a conclusion. As is evident from above data, I am expecting further increase in the cutoff marks for future exams. GATE (CHEMISTRY) GATE exam is conducted once in every year in chemical sciences along with other engineering subjects. It is organized by IIT's and the purpose of this exam is to select candidates who want to pursue their masters courses in technology (M. Tech). The candidates with very good GATE score are also eligible to get the CSIR scholarship in some selected institutes and preferred over others while taking into project work. CSIR NET CHEMITRY SYLLABUS The syllabus for CSIR NET and GATE exams including other exams for Ph.D entrance exams is almost same. The common syllabus for both part B & C of CSIR NET exam in chemical sciences is given below. Inorganic Chemistry :

2. Structure and bonding in homo and hetero nuclear molecules, including shapes of molecules (VSEPR Theory). 3. Concepts of acids and bases, Hard-Soft acid base concept, Nonaqueous solvents. 4. Main group elements and their compounds: Allotropy, synthesis, structure and bonding, industrial importance of the compounds. 5. Transition elements and coordination compounds: structure, bonding theories, spectral and magnetic properties, reaction mechanisms. 6. Inner transition elements: spectral and magnetic properties, redox chemistry, analytical applications. 7. Organometallic compounds: synthesis, bonding and structure, and reactivity. Organometallics in homogeneous catalysis. 8. Cages and metal clusters. 9. Analytical chemistry- separation, spectroscopic, electro- and thermoanalytical methods. 10. Bioinorganic chemistry: photosystems, porphyrins, metalloenzymes, oxygen transport, electron- transfer reactions; nitrogen fixation, metal complexes in medicine.

11. Characterization of inorganic compounds by IR, Raman, NMR, EPR, Mössbauer, UV-vis, NQR, MS, electron spectroscopy and microscopic techniques.

6. Molecular spectroscopy: Rotational and vibrational spectra of diatomic molecules; electronic spectra; IR and Raman activities – selection rules; basic principles of magnetic resonance.

12. Nuclear chemistry: nuclear reactions, fission and fusion, radioanalytical techniques and activation analysis.

7. Chemical thermodynamics: Laws, state and path functions and their applications; thermodynamic description of various types of processes; Maxwell’s relations; spontaneity and equilibria; temperature and pressure dependence of thermodynamic quantities; Le Chatelier principle; elementary description of phase transitions; phase equilibria and phase rule; thermodynamics of ideal and nonideal gases, and solutions.

Physical Chemistry: 1. Basic principles of quantum mechanics: Postulates; operator algebra; exactly- solvable systems: particle-in-a-box, harmonic oscillator and the hydrogen atom, including shapes of atomic orbitals; orbital and spin angular momenta; tunneling. 2. Approximate methods of quantum mechanics: Variational principle; perturbation theory up to second order in energy; applications. 3. Atomic structure and spectroscopy; term symbols; many-electron systems and anti-symmetry principle. 4. Chemical bonding in diatomics; elementary concepts of MO and VB theories; Huckel theory for conjugated p-electron systems. 5. Chemical applications of group theory; symmetry elements; point groups; character tables; selection rules.

8. Statistical thermodynamics: Boltzmann distribution; kinetic theory of gases; partition functions and their relation to thermodynamic quantities – calculations for model systems. 9. Electrochemistry: Nernst equation, redox systems, electrochemical cells; DebyeHuckel theory; electrolytic conductance – Kohlrausch’s law and its applications; ionic equilibria; conductometric and potentiometric titrations. 10. Chemical kinetics: Empirical rate laws and temperature dependence; complex reactions; steady state approximation; determination of reaction mechanisms; collision and transition state theories of rate constants; unimolecular reactions; enzyme kinetics; salt effects; homogeneous catalysis; photochemical reactions. 11. Colloids and surfaces: Stability and properties of colloids; isotherms and surface area; heterogeneous catalysis.

12. Solid state: Crystal structures; Bragg’s law and applications; band structure of solids.

6. Common named reactions and rearrangements – applications in organic synthesis.

13. Polymer chemistry: Molar masses; kinetics of polymerization.

7. Organic transformations and reagents: Functional group interconversion including oxidations and reductions; common catalysts and reagents (organic, inorganic, organometallic and enzymatic). Chemo, regio and stereoselective transformations.

14. Data analysis: Mean and standard deviation; absolute and relative errors; linear regression; covariance and correlation coefficient. Organic Chemistry: 1. IUPAC nomenclature of organic molecules including regio- and stereoisomers. 2. Principles of stereochemistry: Configurational and conformational isomerism in acyclic and cyclic compounds; stereogenicity, stereoselectivity, enantioselectivity, diastereoselectivity and asymmetric induction. 3. Aromaticity: Benzenoid and non-benzenoid compounds – generation and reactions. 4. Organic reactive intermediates: Generation, stability and reactivity of carbocations, carbanions, free radicals, carbenes, benzynes and nitrenes. 5. Organic reaction mechanisms involving addition, elimination and substitution reactions with electrophilic, nucleophilic or radical species. Determination of reaction pathways.

8. Concepts in organic synthesis: Retrosynthesis, disconnection, synthons, linear and convergent synthesis, umpolung of reactivity and protecting groups. 9. Asymmetric synthesis: Chiral auxiliaries, methods of asymmetric induction – substrate, reagent and catalyst controlled reactions; determination of enantiomeric and diastereomeric excess; enantiodiscrimination. Resolution – optical and kinetic. 10. Pericyclic reactions – electrocyclization, cycloaddition, sigmatropic rearrangements and other related concerted reactions. Principles and applications of photochemical reactions in organic chemistry. 11. Synthesis and reactivity of common heterocyclic compounds containing one or two hetero atoms (O, N, S). 12. Chemistry of natural products: Carbohydrates, proteins and peptides, fatty acids, nucleic acids, terpenes, steroids and alkaloids. Biogenesis of terpenoids and alkaloids.

13. Structure determination of organic compounds by IR, UV-Vis, 1 H & 13 C NMR and Mass spectroscopic techniques.

For Part-A, one can go through books on General Aptitude and Logical Reasoning.

Interdisciplinary topics:

For Part-B, you need to be thorough in all the areas of chemistry from 10+2 level to undergraduate level. Everything is important here.

1. Chemistry in nanoscience and technology. 2. Catalysis and green chemistry. 3. Medicinal chemistry. 4. Supramolecular chemistry. 5. Environmental chemistry. PREPARATION (OR) PLAN OF ACTION FOR CSIR UGC NET EXAM Most common question asked by students is "What should be the plan of action to crack CSIR NET exam?" or "How should I prepare for this exam?". My sincere, but very simple, suggestion is to read standard textbooks (see the list of suggested textbooks) and solve old question papers of CSIR, GATE, IISc etc. If you are already done with reading lots of classroom notes and other textbooks then start with solving old question papers. This is the best way to crack any exam. What should be the plan of action?

For Part-C, choose any area of chemical sciences i.e, either organic or inorganic or physical, depending on your taste and specialization at PG level. Always choose right books and solve the previous question papers in a logical manner. Few pupil are also asking for important topics/books, mostly for Paper-C. Following is a possible combination of topics/books you can choose. Paper-A

Paper-B

10+2 NCERT Chemistry Books on General Combination- Aptitude & logical textbooks 1 + reasoning undergraduate level chemistry books

Paper-C

Organic Books

Combination2

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Inorganic Books

3) Inorganic chemistry by Miessler (I like this book for its simple and straight forward explanation.)

Combination3

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Physical Books

4) Inorganic chemistry: Principles of structure and reactivity by James E. Huheey (You will start appreciating inorganic chemistry after reading this book. I enjoyed and learned a lot from this fantastic text book.)

IF YOU STILL HAVE QUESTIONS RELATED TO PREPARATION PLEASE GO THROUGH THE FREQUENTLY ASKED QUESTIONS SECTION. SUGGESTED BOOKS FOR CSIR UGC NET & GATE CHEMICAL SCIENCES The best suggestion to crack any exam is to go through the textbooks written by authorities in the respective fields. Following is a list of textbooks in different areas of chemical sciences. Actual list is very vast. However, it is better to go through only few books that are followed by professors at our universities and IITs.

INORGANIC CHEMISTRY BOOKS 1) Inorganic chemistry by Shriver & Atkins (Suggested by most of Indian Institutues of Technology. Solve the exercises given inside and at the end of each chapter to master this subject.) 2) Inorganic chemistry by Catherine E. Housecroft (Another favorite of IIT professors. The NCERT chemistry textbooks have the material referenced from this book.)

5) Advanced inorganic chemistry by F. Albert Cotton & Geoffrey Wilkinson (Must for an inorganic chemist. But you need lots of patience to feel like a Jargon.) 6) The organometallic chemistry of the transition metals by Robert H. Crabtree 7) NMR, NQR, EPR & MOSSBAUER Spectroscopy in inorganic chemistry by R.V.Parish 8) Biological inorganic chemistry: An introduction by Robert R.Chrichton 9) Bioinorganic chemistry: A short course by Rosette M. RoatMalone

ORGANIC CHEMISTRY BOOKS 1) Organic chemistry by Clayden, Greeves, Warren & Wothers (I think already you know about this famous book. Not only written in

a lucid manner and is very important for those who dare to attempt organic questions from part C of CSIR NET exam. Most of the previous organic questions are straightly from this book. Just enjoy reading this book and earn easy points.)

10) Advanced organic chemistry (Part A & B) by Francis A. Carey & Richard J. Sundberg (Another reference book for organic synthesis) 11) Named organic reactions by Thomas laue & Andreas Plagens

2) Modern methods of organic synthesis by William Carruthers & Iain Coldham (Refer this book for advanced organic synthesis. Another book from which most of the organic questions are dumped into the exam.) 3) Organic chemistry by John McMurry (Must read for basics. Very famous undergraduate book.) 4) Organic chemistry by L.G.Wade, JR (Another book for basics) 5) Advanced organic chemistry by J March (A must reference book) 6) Pericyclic reactions by Ian Fleming 7) Modern organic synthesis: An introduction by Michael H. Nantz (Another good book with straight forward explanations) 8) Spectrometric identification of organic compounds by Robert M. Silverstein 9) Introduction to organic photochemistry by John D. Coyle

PHYSICAL CHEMISTRY BOOKS 1) Physical chemistry by P.W. Atkins & Julio De Paula (Read the book. Solve the exercises & problems given. That is sufficient.) 2) Physical chemistry by Ira N. Levine 3) Physical chemistry by Robert G. Mortimer ANALYTICAL CHEMISTRY Analytical chemistry is not only one of the oldest but very progressive scientific discipline. It plays a very stimulating and essential role in the development of modern scientific and technological world. It deals mostly with the chemical analysis and separation techniques using electroanalytical, spectrochemical and kinetic methods. Analytical chemistry has not only stimulated the development of many fields of science and technology like biology, medicine, archeology, geology etc., and also heavily influenced by other

branches of science like nuclear physics, electronics, instrumentation, material sciences etc. Analytical chemistry is the chemical discipline that employs normal to specialized techniques to gain information on the chemical composition; structure of substances at macro level as well as at molecular and atomic level; and also helps in separation of mixtures of substances. It addresses the problems associated with separation, identification, speciation and quantification of substances. 

Lassaigne's test to detect the presence of nitrogen, sulfur and halogens in organic compounds

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Preparation of Sodium Fusion Extract for Lassaigne's test



Detection of nitrogen



Detection of sulfur

Lassaigne’s test is used to detect the presence of elements: Nitrogen (N), Sulfur (S), Chlorine (Cl), Bromine (Br) and Iodine (I). This test involves following two steps. i) preparation of sodium fusion extract (SFE). ii) Detection of elements using SFE.

i) Preparation of SFE A small amount of organic substance is fused with small quantity of sodium metal in a fusion tube. The red hot fusion tube is then plunged into distilled water and the contents are boiled for a few minutes, then cooled and filtered. The filtrate obtained is called sodium fusion extract (SFE) or Lassaigne’s extract. It is usually alkaline. If it is not alkaline, a few drops of NaOH solution may be added to make it alkaline.

ii) Detection of elements using SFE 

Detection of halogens



Summary sheet LASSAIGNE'S TEST

Thus obtained SFE is used to detect the presence of elements like N,S,Cl, Br & I. The elements in the organic compound react with sodium during fusion reaction as follows:

Na + C + N ------------> NaCN 2Na + S ----------------> Na2S

(if N is present) (if S is present)

Na + S + C + N --------> NaSCN (if both N & S are present & insufficient amount of Na is used) Na + X -------------------> NaX

Note: Conc. HCl is added to convert Ferrous hydroxide, a green precipitate to ferrous chloride, which issoluble in water. Otherwise the green precipitate may interfere with Prussian blue color. Fe(OH)2 + 2HCl --------------> FeCl2 + 2H2O

(If halogens are present)

Where When both N & S are present: X = Cl/Br/I Hence SFE may contain any of or all of ionic forms of respective elements. TEST FOR NITROGEN To a portion of SFE, freshy prepared ferrous sulphate, FeSO 4 solution is added and warmed. Then about 2 to 3 drops of FeCl 3 solution are added and acidified with conc. HCl. The appearance of a Prussian blue color indicates the presence of nitrogen.

However if both N & S are present in the organic compound and SFE is prepared with insufficient amount of Na metal, the thiocyanate (SCN-) is formed instead of cyanide ion (CN -). The thiocyanate, SCN- reacts with Fe3+ to give a blood red coloration due to formation of [Fe(SCN)]2+. Fe3+ + SCN– -------------> [Fe(SCN)]2+ Note: However, if sodium fusion is carried out with excess of sodium, the thiocyanate, SCN- is decomposed to give CN – & S2–. Hence in this case, sulfur and nitrogen are to be identified in separate tests. TEST FOR SULFUR i) The appearance of a deep violet color upon addition of a few drops of sodium nitroprusside to SFE indicates the presence of sulfur.

ii) The formation of a pale yellow precipitate that is partially soluble in NH4OH confirms the presence of bromine. ii) Sulphur can also be detected by adding lead acetate to SFE, acidified with acetic acid. The formation of a black precipitate (PbS) indicates the presence of sulfur. iii) Where as the formation of a yellow precipitate insoluble in NH4OH confirms the presence of iodine in the organic compound.

TEST FOR HALOGENS The sodium fusion extract, SFE can be used to detect the presence of chlorine, bromine and iodine but not fluorine. To detect their presence, the SFE is first acidified with HNO3 and then added with AgNO3 solution. i) The formation of a curdy white precipitate that is soluble in NH4OH indicates the presence of chlorine in the organic compound.

Note: 1) It is not possible to detect the presence of fluorine since the solubility of AgF is more and thus no precipitate is formed. 2) If nitrogen or sulfur are present in the organic compound, the formation of black precipitates of AgCN or AgS may interfere during the test for halogens. Hence the CN - and S2- have to be removed from the SFE. This is done by boiling the SFE with conc. HNO3 or glacial acetic acid to almost dryness. The CN - and S2- ions are removed as HCN and H2S gases.

SUMMARY SHEET OF LASSAIGNE'S TEST Test Observation Inference

SFE + FeSO4 + FeCl3 + HCl

i) SFE + Sodium nitroprusside

i) Nitrogen is i) A prussian blue color is confirmed. formed. ii) Both nitrogen ii) Blood red coloration is and sulfur are observed. confirmed. i) A violet coloration is observed.

ii) SFE + CH3COOH ii) A black precipitate is + Pb(CH3COO)2 formed.

Sulfur is confirmed.

SFE + HNO3 + AgNO3

i) A white ppt. soluble in NH4OH is formed. i) Chlorine is confirmed. ii) A pale yellow ppt. partially soluble in ii) Bromine is NH4OH is formed. confirmed. iii) A yellow ppt. insoluble in NH4OH is formed.

iii) Iodine is confirmed.