BSCCH- 302 B.Sc. III YEAR ORGANIC CHEMISTRY-III SCHOOL OF SCIENCES DEPARTMENT OF CHEMISTRY UTTARAKHAND OPEN UNIVERSITY ORGANIC CHEMISTRY-III BSCCH-302 BSCCH-302 ORGANIC CHEMISTRY III SCHOOL OF SCIENCES DEPARTMENT OF CHEMISTRY UTTARAKHAND OPEN UNIVERSITY Phone No. 05946-261122, 261123 Toll free No. 18001804025 Fax No. 05946-264232, E. mail [email protected] htpp://uou.ac.in UTTARAKHAND OPEN UNIVERSITY Page 1 ORGANIC CHEMISTRY-III BSCCH-302 Expert Committee Prof. B.S.Saraswat Prof. A.K. Pant Department of Chemistry Department of Chemistry Indira Gandhi National Open University G.B.Pant Agriculture, University Maidan Garhi, New Delhi Pantnagar Prof. A. B. Melkani Prof. Diwan S Rawat Department of Chemistry Department of Chemistry DSB Campus, Delhi University Kumaun University, Nainital Delhi Dr. Hemant Kandpal Dr. Charu Pant Assistant Professor Academic Consultant School of Health Science Department of Chemistry Uttarakhand Open University, Haldwani Uttarakhand Open University, Board of Studies Prof. A.B. Melkani Prof. G.C. Shah Department of Chemistry Department of Chemistry DSB Campus, Kumaun University SSJ Campus, Kumaun University Nainital Nainital Prof. R.D.Kaushik Prof. P.D.Pant Department of Chemistry Director I/C, School of Sciences Gurukul Kangri Vishwavidyalaya Uttarakhand Open University Haridwar Haldwani Dr. Shalini Singh Dr. Charu Pant Assistant Professor Academic Consultant Department of Chemistry Department of Chemistry School of Sciences School of Science Uttarakhand Open University, Haldwani Uttarakhand Open University, Programme Coordinator Dr. Shalini Singh Assistant Professor Department of Chemistry Uttarakhand Open University Haldwani UTTARAKHAND OPEN UNIVERSITY Page 2 ORGANIC CHEMISTRY-III BSCCH-302 Unit Written By Unit No. Dr. Charu Pant 01, 02 & 03 Department of Chemistry Uttarakhand Open University Haldwani Dr. Girdhar Joshi 04 & 05 Depatment of Chemistry P.G. College Gopeshwar Dr. Bipin Chandra Joshi 06 & 09 Department of Chemistry LSM Govt. PG College Pithoraghar Dr. Devendra Singh Dhami 07 & 08 Department of Chemistry SSJ Campus, Almora Dr. Neelam Kumari 10, 11, 12 & 13 Department of Chemistry Meerut College, Meerut Course Editor Dr. Charu Pant Academic Consultant Department of Chemistry School of Science Uttarakhand Open University Title : Organic Chemistry III ISBN No. : Copyright : Uttarakhand Open University Edition : 2019 UTTARAKHAND OPEN UNIVERSITY Page 3 ORGANIC CHEMISTRY-III BSCCH-302 CONTENTS Block-I NMR and Organometallic compounds Unit 1 NMR Spectroscopy 5-32 Unit 2 Organometalic Compounds 33- 43 Unit 3 Organisulphur Compounds 44-56 Block -2 Heterocyclic Compounds Unit 4 Heterocyclic Compounds -I 57-96 Unit 5 Heterocyclic compounds II 97-125 Block -3 Biomolecules-I Unit 6 Amino acids, Peptides, Proteins 126-163 Unit 7 Carbohydrates-I 164- 193 Unit 8 Carbohydrate- II 194-216 Unit 9 Lipids 217-243 Block-4 Bimolecular-II Unit 10 Nucleic acids 244-261 Unit 11 Fats Oils and Detergents 262-277 Unit 12 Synthesis Dyes 278-296 Unit 13 Natural Products 297-331 UTTARAKHAND OPEN UNIVERSITY Page 4 ORGANIC CHEMISTRY-III BSCCH-302 UNIT 1: NMR SPECTROSCOPY CONTENTS: 1.1 Objectives 1.2 Introduction 1.3 Proton magnetic resonance ( 1H NMR) spectroscopy 1.3.1 Phenomena of energy absorption (Resonance & relaxation phenomena) 1.3.2 Nuclear shielding and deshielding 1.4 Chemically equivalent & Non-equivalent protons 1.5 Chemical shift 1.5.1 Chemical shift parameters 1.5.2 Internal standard for NMR spectroscopy 1.6 Spin-spin splitting and coupling constants 1.7 Area of signals 1.8 Applications of NMR Spectroscopy 1.9 Interpretation of PMR spectra of simple organic molecules e.g. Ethyl bromide, ethanol, acetaldehyde, 1, 1, 2-tribromoethane, ethyl acetate, toluene and acetophenone. 1.10 Problems pertaining to the structure elucidation of simple organic compounds using UV, IR and PMR spectroscopic techniques. 1.11 Summary 1.12 Terminal Question 1.13 Answers 1.1. OBJECTIVES • Give a brief description of NMR, including what peaks represent, and what you can learn about a compound. • Know how nuclear spins are affected by a magnetic field • What happens when radiofrequency radiation is absorbed UTTARAKHAND OPEN UNIVERSITY Page 5 ORGANIC CHEMISTRY-III BSCCH-302 • Use a list of common chemical shift ranges to predict the range of H's in various functional groups. • Be able to predict the number of proton NMR signals expected from a compound given its structure. • Be able to predict the splitting pattern in the proton NMR spectrum of a compound given its structure. • Be able to use NMR spectra to determine the structures of compounds, given other information such as a molecular formula. • Be able to calculate coupling constants from 1H NMR spectra, and utilize the coupling constants for determining compound structure. • Be able to determine the compound structure based on information generated from mass spectrometry, IR, NMR, and elemental analysis. 1.2. INTRODUCTION The concept of NMR was represented at first in 1946 by two groups of eminent physicist; Black Hensen and Packard at Stanford University detected a signal from the Protons of water and Parcell, Torrey and pound at Havard University observed a signal from the photons in Paraffin wax. Black and Parcell were jointly awarded a Nobel Prize for Physics in 1952 for this discovery. NMR spectroscopy involvers transition of a nucleus from one spin state to other with the resultant absorption of electromagnetic radiation by spin active nuclei (having nuclei spin not equal to zero) when they are placed in magnetic field. Nuclear magnetic resonance spectroscopy related to the nuclei and only one type of nucleus at a particular timeline. 1H or C 13 , F 19 when the frequency of the rotating magnetic field and that of the processing nucleus(Lamar Frequency) become equal, they are said to be in resonance absorption or emission of energy by the nucleus can be obtained. Plot of the peak intensities versus the frequencies of objection (represented by δ or τ) establish an NMR spectrum. The 1H nucleus is most commonly studied by NMR spectroscopy because of its high natural abundance (99.98%) and the fact that it is present in the majority of organic compounds, the PMR or 1H NMR spectrum provides information about the number of different types of protons and also the chemical environment of each of them. UTTARAKHAND OPEN UNIVERSITY Page 6 ORGANIC CHEMISTRY-III BSCCH-302 A simple representation of NMR spectrum can be given as: TMS Intensity δ Figure: 1.1 A simple representation of NMR spectrum 1.3. PROTON MAGNETIC RESONANCE ( 1H NMR) SPECTROSCOPY 1HNMR or PMR spectroscopy is the most widely applicable Nuclear Magnetic Resonance spectroscopy for the structural determination of various organic compounds but the other NMR spectroscopic methods like C13 and P31 NMR spectroscopy; F19 spectroscopy can also be helpful in the structural determination of the compounds. Spin active nuclei: All those nuclei which having the full integer or half integer nuclear spin value are known as spin active nuclei. With the help of the number of the electron/proton and neutron in the various nuclei, the spin active or inactive nature for them can be defined as: e-/p Neutron (n) Nuclear spin (I) Nuclei Examples 16 Even Even 0 Inactive 8O 14 12 Odd Odd Full integer Active 7N , 6C 13 Even Odd Full integer Active 6C 31 1 Odd Even Half integer Active 15 P , 1H 1.3.1. Phenomena of energy absorption (Resonance & relaxation phenomena): UTTARAKHAND OPEN UNIVERSITY Page 7 ORGANIC CHEMISTRY-III BSCCH-302 In the absence of external magnetic field H 0 the nuclear spin are randomly oriented, However when the sample is placed in an external magnetic field then the nuclei (proton) with the spin +half (1/2) are aligned with the applied field in that lower energy α- spin stagehand the nuclei with the spin -1/2 are aligned against to the external magnetic field in the higher energy β- spin state that can be represented as: β−-spin state (I= -1/2) H0 ∆E Random arrangement of spin α-spin state H (I= +1/2) active nuclei in the absance of H0 0 Figure 1.2. Orientation of spinning nuclei in absence and presence of external magnetic field The value of energy difference b/w and spin state depends on the strength of external magnetic field H0 according to the equation during the PMR spectroscopy, and then it can be represented as: β-spin state ∆E E α-spin state H0 Figure 1.3. Energy states of nuclear spin Thus according to above spin states resonance phenomena may be defined as the transition of spin active nuclei from state to the state by the absorption of Rf radiation while UTTARAKHAND OPEN UNIVERSITY Page 8 ORGANIC CHEMISTRY-III BSCCH-302 the phenomena of returning the spin active nuclei from high energy β- spin state to the low energy α-spin state is known as relaxation phenomena. Both the resonance and relaxation phenomena can be represented as: β -spin state Resonance Relaxation Phenomena Phenomena α-spin state Figure 1.4. Resonance and Relaxation 1.4. NUCLEAR SHIELDING AND DESHIELDING Electron surrounding the spin active nuclei can also generate their own magnetic field which is called as induced magnetic field, that oppose the applied magnetic field in the region of the nucleus and these e - which generate their induced magnetic field are known as diamagnetic e - and this effect on the nucleus by these e - is known as diamagnetic shielding. Nucleus Induced magnetic field by the e- H0 Figure 1.5. Shielding and deshielding of a nucleus The external magnetic field is uniform over the entire molecule and therefore cannot differentiate to the different types of the proton. However the induced magnetic field generated by the e- around the nucleus is not uniform, this situation makes the different spin active nuclei 9proton) to be non-equivalent. Thus each proton in the different electronic environment show slightly different magnetic field due to the circulation of e- in the neighboring bond.