2nd Midterm Test CHEM 2220 GC PDF

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Covers all chapters up till chapter 6 or lecture 17...

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ONTARIO TECH UNIVERSITY SECOND YEAR 2nd MID TERM TEST WINTER 2021

Molecular Structure CHEM 2220 CRN 73916 Date: 26th March 2021 Marks: 50

Time: 95 minutes

Name of Student: __Kuganesh Ketheesh____________________ Banner ID: ___100598968_________________ Instructions: 1. Attempt all questions. There are two parts in total (MCQs and short questions). 2. Read all questions carefully, answer the questions using the provided space. 3. There are 13 pages in total including this page.

Part A Part B Total

PART A

MCQs Short Questions

10 40 50

(10 Marks)

Multiple Choice Questions: 1. For the proton NMR, the higher is the electron density of surrounding electrons, a., the higher is the chemical shift. b. the downfield the signal would be. c. the higher is the larmor frequency. d. the resonance will occur at lower radiofrequency. 2. Which of the following molecules are associated with magnetic anisotropy? a. Pentene b. Toluene c. Acetylene d. Ethane 3. In the 13C{1 H} NMR spectrum, what does the solvent 13C resonance appear as in CDCl3 solution? a. Singlet b. 1:1 Doublet c. 1:2:1 Triplet d. 1:1:1 Triplet 4. The counter magnetic field generated by the circulating electrons in an applied magnetic field, surrounding the protons is called a. Diamagnetic de-shielding b. Local diamagnetic current c. Diamagnetic shielding d. None of the given options 5. What is the minimum chemical shift separation in ppm at 300 MHz to ensure a first order spectrum if the resonances are coupled to each other with a 12 Hz coupling constant? a. 25 b. 0.04 c. 300 d. 12

6. The peak intensity ratio in a quartet is

a. 1:2:2:1 b. 1:3:3:1 c. 2:3:3:2 d. 1:1:1:1 7. A proton coupled C-13 spectra shows a. Homonuclear coupling b. Heteronuclear coupling c. Both of these d. None of these 8. The value of coupling constant between two protons, a. Increases by increasing the strength of applied magnetic field b. Increases by decreasing the strength of applied magnetic field c. Decreases by decreasing the radiofrequency of spectrometer d. None of these 9. Which of the following will show a -ve signal (↓) in the 13C DEPT-135 spectrum? a. Tertiary butane b. Aniline c. 2,4-cyclopentdien-1-ol d. 1,4-cyclohexdiene 10. In the given compound, how many (I) 13C NMR signals, (II) the number of enantiotopic protons, and (III) the number of diastereotopic protons are there respectively?

a. (I) =6, (II) =0, (III) = 2 b. (I) =5, (II) =2, (III) = 0 c. (I) =5, (II) =0, (III) = 2 d. (I) =6, (II) =2, (III) = 0 PART B; Short Questions

(40 Marks)

1. For the following pairs of molecules, explain how you would use Proton NMR and C-13 NMR to distinguish between them. 6 Marks

2. Consider the molecule below. Label each type of proton as a, b, c etc. and name the predicted splitting pattern it would exhibit in a 1H NMR spectrum. Draw the tree diagram for each type of proton. Ignore the possibility of LongRange Coupling. 8 Marks

H O

H H

CH2OH H

H

3.The 1H and

13C NMR spectra of oxygen-containing compound (C6H12O2) is given below. Identify the compound. Be sure to explain below how you determined the structure of the molecule discussing each technique presented. 8 Marks

4.Given is the IR, Proton NMR, C-13 and DEPT spectra of compound with molecular ion peak reported at m/z = 84. Identify the structure of this compound. Be sure to explain below how you determined the structure of the molecule discussing each technique presented. 10 Marks

5.Mention are the splitting patterns of two different protons H B and HC with given chemical shifts in ppm (spectrometer frequency = 60 MHz). Draw the splitting tree diagram for protons HA and HB, name the splitting patterns, calculate coupling constants. Are these two protons splitting each other, justify. (Consider the presence of other types of protons too e.g. Ha etc when drawing splitting tree diagram). 8 Marks...