Indian Forest Service (Mains)
Chemistry optional
- 2 papers
- 200 marks each
- 3 h per paper
Paper I covers physical and inorganic chemistry.
Coordination chemistry: every question, 2021 to 2025
27 parts worth 242 marks have been set on this unit in UPSC IFoS Chemistry Paper I from 2021 to 2025. Each one opens on its own page with the question, the answer in brief and the key points.
(a) Electronic configurations; introduction to theories of bonding in transition metal complexes. Valence bond theory, crystal field theory and its modifications; applications of theories in the explanation of magnetism and electronic spectra of metal complexes. (b) Isomerism in coordination compounds. IUPAC nomenclature of coordination compounds; stereochemistry of complexes with 4 and 6 coordination numbers; chelate effect and polynuclear complexes; trans effect and its theories; kinetics of substitution reactions in square-planar complexes; thermodynamic and kinetic stability of complexes. (c) Synthesis and structures of metal carbonyls; carboxylate anions, carbonyl hydrides and metal nitrosyl compounds. (d) Complexes with aromatic systems, synthesis, structure and bonding in metal olefin complexes, alkyne complexes and cyclopentadienyl complexes; coordinative unsaturation, oxidative addition reactions, insertion reactions, fluxional molecules and their characterization. Compounds with metal-metal bonds and metal atom clusters.
Notes: Crystal field theory (full notes) · short notes
Notes: Werner theory, isomerism, IUPAC names and VBT of complexes (full notes) · short notes
Notes: Organometallics: 18-electron rule, oxidative addition, Wilkinson's catalyst (full notes) · short notes
Notes: Metal carbonyls, nitrosyls, 18-electron rule and metal clusters (full notes) · short notes
Notes: Substitution in complexes: labile and inert, trans effect, stability constants (full notes) · short notes
Notes: Electronic spectra of complexes: term symbols, selection rules, charge transfer (full notes) · short notes
2025
- Q5(c) Hexaamminechromium(III)8 marks Answered
- Q5(d) Dicobalt octacarbonyl8 marks Answered
- Q7(b) Coordination nomenclature10 marks Question only
- Q7(c)(i) Colour of iron(II) complexes5 marks Question only
- Q7(c)(ii) Dichloridobis(oxalato)chromate(III)10 marks Question only
- Q8(a)(i) Alkyne–dicobalt bonding10 marks Question only
- Q8(a)(ii) Alkene insertion into metal bonds5 marks Question only
2024
- Q5(b) Isomers of a cobalt A₂B₂C₂ complex8 marks Answered
- Q5(c) Dicobalt octacarbonyl and infrared bands8 marks Answered
- Q6(a) Magnetism and colour of Co(II) complexes15 marks Question only
- Q7(b)(i) Hydrogen addition to Vaska complex5 marks Question only
- Q7(b)(ii) Fluxionality of tetracyclopentadienyltitanium10 marks Question only
2023
- Q5(c) Normal and inverse spinels8 marks Answered
- Q5(d) All stereoisomers of the nickel glycinate complex8 marks Answered
- Q7(b) Structure of dimanganese decacarbonyl15 marks Question only
- Q7(c) Platinum–alkyne bonding10 marks Question only
- Q8(a) Concerted and SN2 oxidative addition10 marks Question only
2022
- Q5(c) Oxidation of cobalt ammine8 marks Answered
- Q5(d) Absorption bands of aqueous V(III)8 marks Answered
- Q6(c)(i) Octahedral and tetrahedral splitting8 marks Answered
- Q6(c)(ii) Magnetism of octahedral and tetrahedral Ni(II)7 marks Answered
- Q7(b)(i) Square-planar substitution and trans effect10 marks Question only
- Q7(b)(ii) Fluxional molecules and variable-temperature NMR5 marks Question only
2021
- Q5(d) Effective atomic number rule8 marks Answered
- Q6(c) Cis and trans dichlorotetraamminecobalt(III)10 marks Answered
- Q7(c) Pi donors and acceptors in octahedral complexes10 marks Question only
- Q8(a) Structures from coordination names15 marks Question only
UPSC Indian Forest Service (Main) Chemistry Paper I: Model Answers 2021 to 2025
- All eight questions of each paper, with the question printed above its answer
- Physical chemistry numericals worked with units; inorganic structures drawn
- Topic-wise weightage and a topic-wise index