Chemistry Questions and Answers August 26, 2020

The solubility product of Ag2C2O4 at 25C is 1.29 x 10-11 mol3L-3. A solution of K2C2O4 containing 0.520 moles in 500mL water is shaken at 25C with an excess of Ag2CO3 till the following equilibrium is reached; Ag2CO3 + K2C2O4 ? Ag2C2O4 + K2CO3 At equilibrium, the solution contains 0.0358 moles of K2CO3. Assuming the degree of dissociation of

For the reaction; PCl5(g) ? PCl3(g) + Cl2(g) The forward reaction at constant temperature is favoured by: (A) Introducing an inert gas at constant volume (B) Introducing chlorine gas at constant volume (C) Introducing an inert gas at constant pressure (D) Increasing the volume of the container (E) Introducing PCl5 at constant volume

The correct statement(s) for cubic close-packed (ccp) three-dimensional structure is (are) A. The number of the nearest neighbours of an atom present in the topmost layer is 12 B. The efficiency of atom packing is 74% C. The number of octahedral and tetrahedral voids per atom are 1 and 2, respectively D. The unit cell edge length is 2?2 times the

If the unit cell of a mineral has a cubic close-packed (ccp) array of oxygen atoms with m fraction of octahedral holes occupied by aluminium ions and n fraction of tetrahedral holes occupied by magnesium ions, m and n, respectively, are: (A) , ? (B) 1, (C) , (D) , ?

The packing efficiency of the two-dimensional square unit cell shown below is: (A) 39.27% (B) 68.02% (C) 74.05% (D) 78.54%

6. Rank the rotation barriers relative to the indicated bonds, with 1 have the largest barrier For convenience, Et ethyl and iPr isopropyl Assume that a halogen, OH, or NH is smaller than a CH3 or any other alkyl group. Et iPr Et Et Et the Et Et iPr

a. For each, note if any total eclipse steric interactions exist (two nonhydrogens eclipsing) b. For each, note if any gauche steric interactions exist (two nonhydrogens gauche),7. 8. 9. 11. 12. H H 10. H H 13. H H H CH3 F CH3 CH3 HC H CH3 H H CH3 H H3C, H H CH3 H H H iPr IH H H CH3 H H H H CH3 CH3 iPr H CH3 H H H H H H H H H H CH H CH3 H CH3 H

D. Newman Projection Energy Diagrams. 14. Draw a qualitative energy diagram for CH3CHCHCH(CH3)2, relative to the bond between the two CH2 carbons. The Newman projections are drawn below, using iPr as an abbreviation for the isopropyl CH(CH3)2 group. Put S (for staggered) by any staggered conformation, and E (for eclipsed) by an eclipsed

15. Draw a qualitative energy diagram for CH3CHCH(CH3)2, relative to the C2C3 bond. The Newman projections are drawn below. CH CH3 CH CH CH3 H H H CH3 CH3 CH3 H H CH3 CH H CH3 H3C CH3 H CH3 HC H CH3 H H CH3 H CH CH3 QipHs

B. Identify each of the following molecule as chiral or achiral. (By circling the chiral ones.) Write meso where it applies. (In other words, if it is achiral despite having chiral centers). H OH 31. 34. 37. 40. 42. 44 46. 49. NTO HCO H CH3 . CI H OH H OH OH OH 32. SS 45. 50 Hh HC H H.L H OH CH H CI CI HE Br OH H NH 33. 36. 39. 48. H3C H

2. Provide the proper IUPAC name for the alkene shown below.

Choose the most stable alkene among the following. (may help to draw each of them out first...) a. 1methylcyclohexene b. 3methylcyclohexene c. 4methylcyclohexene d. They are all of equal stability

For each of the following reactions, write whether the mechanism would be radical, cationic, or anionic?

1. 2. ON 3. 4. 5. 6. 7. 8. 9. HNO3 Br NaOH CH3OH, H Br2, peroxides Br, NaOH HO, H peroxides ON H3COOCH3 HO, H H3CO OCH3 H OH NO etc Br OLI LICH3 I f CH3 Br OH OH .etc

3. Draw the major product for the reaction shown. (There may be some side products or isomers formed in addition to the major products, but you dont need to draw them.) Draw the mechanism. H, HO

Draw the major product for the reaction shown. Include stereochemistry. Draw the mechanism, and make sure it accounts for the product stereochemistry. Br2

Products A and B combine to make up over 90 of the product mixture. a. For each of the structures AD, attach an H atom to the carbon that in fact added an H. b. Classify each of the four structures as either a 1,2 or 1,4 addition product. c. Draw the resonance structures for the cation that leads to both products A B, and also draw the resonance

Draw the two major products for the following reaction. Identify each as either a 1,2 or 1,4 addition product. Write either thermodynamic or kinetic underneath each one. Draw the two resonance structures for the intermediate from which both form. 1.0 HBr .

A. Provide reagents for the following transformations. 1. 2. 3. 4. 5. 6. 7. Br Br OH Br Br HO OH HO OH OH

Aromatic Substitution Reaction Mechanisms Draw the major product and the mechanism for each of the following reactions, using detailed arrowpushing. Draw the resonance structures for carbocationic intermediate. Note See pages 3 and 4 for more production prediction problems. See page 5 for some synthesis design problems. 1. Cl, AICI 1

Draw the major product for the following reactions. Br, FeBr3 1. 2. 3. CI HN NO 1. HNO3, HSO4 2. Br, FeBr 3. Fe, HCI 1. HNO3, HSO4 2. Fe, HCI 3. Br, FeBra Cl AICI 3

Draw a 3-dimensional picture for the atoms in CH3CO2CH2NHCH3, using the hash-wedge convention. (You neednt specify lone pairs, and orbitals need not be shown). (5pt)

14. Classify the relationship between the pairs of molecules as either (8pt) structural isomers same compound geometric isomers resonance structures not isomers (different molecular formulas) H CH3 HH CH3 H OH CH3 H H CH3H Br 31 17.01 OH H H Br H OH

Identify all the funtional groups in the following molecules. (Do not include alkane, since that isnt functional.) (6pt) gak hol

For the following Newman projections, rank them in stability from 1 to 4, 1 being most stable. Identify the anti conformation, the gauche conformation, and the totally eclipsed conformation. (6pt) CH3 H3 CH3 H3 H. H CH3 CH3 H H H CHH TH

Draw any 6 of the 9 possible structural isomers for alkanes with formula C7H16. When deciding whether to draw cyclic or acyclic alkanes, make sure that you fit the formula! Be careful not to draw the same isomer twice! I will take off points for duplicating! (You can try to show off by getting more than 6, but if you do still be sure you dont

Draw the mechanism for the following reaction, and write slow next to the rate determining step. Be sure to draw all intermediates, and to correctly draw electron movement arrows or halfarrows. (Show the propagation steps only.) (4 points) Br hv H Br HBr

Draw the mechanism for the following reaction, and write slow above the rate determning step. Be sure to draw all intermediates, and to correctly draw electron movement arrows. (5 points) H (catalyst) CH3OH (solvent) heat Br HOCH3 HBr

Draw the substitution products for the following reactions. (Do not draw the accompnaying elimination products). Include stereochemistry in your answer, and if two substitution products are formed draw them both. (4 points each),HT (a) H3C H b) H3C CI H CI CH3 NaOH H20 H2O cat. HCI H2O

5a. Put a 1 by the reaction for which AH Eact. b. Put a 2 by the reaction for which Eact 0. c. Put a 3 hy the reaction for which Eact AH. BrBr Br Br. (Eact activation energy) H3CH Br H3C HBr H3C CH3 H3CCH3

Draw the major product for the following reaction. Then draw the mechanism for its formation. (Draw the propagation steps only.) Is your product chiral (You may need to add relevant hydrogens.) Brz hv

Draw all of the different isomers of 2,3-dichlorobutane, identify each as either chiral or meso, and classify the relationship between each two as enantiotopic or diastereotopic. (You may use Fischer projections or zig/zag/hash/wedge pictures, as you please. (If two are the same, cross one of them off your list.)

a.) Draw the two chair conformations of cis3methyl1isopropylcyclohexane. (You dont need to show the Hs on carbons other than 1 and 3). For convenience, you may abbreviate methyl as Me and isopropyl as iPr b.) Circle the more stable conformation. c) Would isomer trans3methyl1isopropylcyclohexane be more stable or less stable than the cis

Draw all possible elimination products that could form from the following reactant. Circle the one that forms in greatest yield. (5 points)

Br

a) Draw all unique stereoisomers of 2,4-dibromopentane. Label each with a letter, A, B, etc.. Cross out any duplicates. (8 points) b) Identify any that are chiral c) Identify any that are meso

Write Lewis structures and assign any nonzero formal charges. a. CH3OH b. CH3COCHON c. CH3CHCHCONH2

Draw a 3-dimensional picture for all of the atoms (hydrogens included) in the molecule CH3CHCHCOCH2CH2NHCH3. Your picture should use the hash-wedge convention to illustrate atoms that are not in the plane of the paper, and should reflect approximate bond angles.

Draw a 3-D picture of CH2O showing the bond as well as the four atoms.

Draw the Newman projections for the best and worst conformations of butane, and give the names for these conformations. Briefly explain what strain factors make the worst conformation worse than the best conformation.

a.) Draw both chair conformations of cis-1-methyl-2-isopropylcyclohexane. Draw the substituents and H-atoms attached to carbons 1 and 2. (You don't need to show the H's on the other carbons). (4pt) b.) Circle the more stable conformation.

A single unknown reacts with O3/Me2S to give the following three products. What is the structure for the unknown?

1. 03. 2. MeS

Draw the major product. 1. BH3 THF 2. H02, OH

Predict the major product in each of the following reactions. stereochemistry stereochemistry is involved in each of these problems a. b. d. Br2, HO Os04 HO 1. BH3THF 2. HO, NaOH CH3CO3H, HO Pay careful attention to (3 points each)

When potassium chlorate (KCIO3) is heated, oxygen gas and solid potassium chloride are produced. 1. How many moles of oxygen form in the balanced chemical equation. 2. Classify the reaction.

When solutions of sodium bicarbonate and nitric acid are mixed, bubbling occurs, condensation on the side of the test tube above the mixture is observed. 5. What is the name of the gas that formed in the reaction as evidenced by the formation of bubbles 6. What is the mole ratio of the reactants 7. in addition to the gas and water, what is the

Mixing of sodium chloride and lead(II) nitrate produces a white precipitate and an aqueous solution. 3. Give the name of the precipitate 4. Classify the reaction T I I

potassium lodide Solubility Graph potassium nitrate chioride potassium chore,A 50 cm sample of water completely dissolves 22 g of an unknown solute at 20C Which compounds are the possible identities of the solute Check all that apply. No partial credit will be given.

Polymers may be composed of thousands of monomers. Draw two repeat units of propene Assume there are hydrogen atoms on the two el of the dimer. Ignore stereochemistry. Ignore inorganic byproducts. A or Av (PhCO2)2 (radical initiator)

What is the experimental yield (in grams) of the solid product when the percent yield is 89.5 when 1.932 g of barium chloride reacts in solution with excess sodium phosphate BaCl2(aq) Na3PO4(aq) 3(PO4)2(s) NaCl(aq) unbalanced What is the percent yield of the solid product when 18.77 g of iron(III) nitrate reacts in solution with excess sodium

The initial in a first order reaction is 0.860 M. concentration after 5 What will be its halflives have passed concentration of a reactant

Bromide B has normal reactivity (for a 2 bromide) toward S1 substitution, but A has much higher reactivity and C has much lower reactivity. a) Why is A more reactive toward S1 b) Why is C much less reactive toward S,1 (4 points) Br Br A B Br Kinetic reactivity toward SN1 reactivity (HO, H)

Synthesis Reactions. Draw the feature product of the following reactions (need not show any byproducts). (21 points, 3 points each) HNO3, HSO4 HO 02 QT CH0 1. HNO3, HSO4 2. Cl, AICI, 3. Fe, HCI 1. C 1. Br.hv 2. NEt3, heat CN 1. SO, HSO4 2. Br, FeBr 3. HO, HSO4 2. Zn(Hg), HCI 3. SOH toate AICI CI, AICI (1 equivalent)

Design a synthesis for the following molecule beginning with toluene.) (6 points) Br ON COH

a) Draw the major product for the following reaction, and b) draw the mechanism for its formation. c) Identify the slow step. d) Draw all the resonance structures for the cation intermediate and e) circle the most important contributor. (7 points) Cl, AICI HN

What is the rate constant of a first order reaction when 20.0 of a reactant remains after 89.0 s

The zero order reaction A Products takes 63.5 minutes for the concentration of A to decrease from 0.970 M to 0.269 M. What is the value of k for this reaction

Predict the major product in each of the following reactions. Pay careful attention to stereochemistry (3 points each) Br H, Pt Cl, HO OSO4, HO2

Draw the product for the following reaction and draw the mechanism for its formation. Identify the slow step. Draw all the resonance structures for the cation intermediate and circle the most important contributor. (7 points) NO Me Br2, FeBr3 H

Provide names or structures for the following. 3 points each. Note dont forget to specify stereochemistry a. b. d. H3C Br OH CH3 optically actve OH f. trans1bromo3isopropylcyclopentane 3

Draw at least four different isomers for C5H10. (There are lots more than four)

Draw the substitution products for the following reactions. (Do not draw any accompanying elimination products.) Include stereochemistry in your answer, and if two substitution products are formed, draw them both. Assume the starting material is optically active as drawn. (3 points each) a. b. Ph H Br Me, Br Ph NAOMe HO, cat. HBr

a. b. C. d. e. ON f. Draw the major product for each of the following reactions. (3 points each, 21 total, 7 minutes) NO g. Br OCHCH Br Cl, AICI, 1. SO3, HSO4 2. HNO3, HSO4 3. HO, HSO4 1, HNO3, HSO4 2. Fe, HCI less active Br MeOC Br, hv 2. NaOMe 1. Mg, ether 2. Br more active CH3 COMe heat Cl2, FeCl3

3. Predict the major products for the following reactions. Pay careful attention when orientation is a factor. Draw just one major product in each case. (3 points each) OCH3 Br CN Br, hv CN NaOCH 1.03 2. MeS HBr OSO4, HO2 1. Br, FeBr3 2. Zn(Hg), HCI 3. Br, hv 1. HO, Hg(OAC)2 2. NaBH4

Draw the products of the following multistep sequences. (4 points each) Me, Br Ph CH3 OH 1. NaOH 2. HBr, peroxides 3. Na Me 1. SO3, HSO4 2. 2bromopropane, AlCl3 3. HO, H 1. HSO4 2. HBr, Peroxides 3. NE13

What are the chemical and structural characteristics of the following.

1. CI

Br Name the following molecules. JS 2 2

Provide products for the following reactions (include all stereoisomers). Indicate if the products are achiraloptically inactive (A) racemicoptically inactive (R), mesooptically inactive (M) or chiraloptically active (C). a) Et Me Et b) Me Et Me 1. Hg(OAc)2, MeOH 2. NaBH4 Et mCPBA

a) b) Show the product(s) of each reaction. Ignore stereochemistry. FCH CECH 1.0 2. DMS HgSO4, HSO4, HO

F. a) Provide the major product of each reaction. Include stereochemistry. b) c) Br, HO H, PdC 1. BH3, THF 2. HO, NaOH

Provide the mechanism and major product for each of the following reactions. Ignore stereochemistry. a) b) HBr HBr, ROOR

Propose a mechanism for the following reaction. Ignore stereochemistry. Br Br Br

b) 03 010,a) R Provide mechanisms for the following reactions. Ignore stereochemistry. R R HO, NaOH 3 ROH B(OH)3

(b) Indicate how many states exist in each band on your diagram (c) Indicate how many electrons occupy each band on your diagram (d) Is sodium a conductor, semiconductor or insulator? Justify your answer with reference to your band diagram

2. (a) E Consider a piece of sodium. Use the symbol N to represent the number of sodium atoms.7 marks Draw a band diagram for sodium. Indicate the atomic orbital(s) that contributed to the band(s) in your diagram. 3 marks II 3s 2p 2s 1s

(e) Draw the MOS. Show both a top view and a side view for each MO. Label each picture so that it is clear which MO it shows. 6 marks,(a) (b) (c) (d) Draw a Lewis diagram (with resonance structures, if appropriate) of NO. Include any nonzero formal charges on the appropriate atom(s). Use VSEPR theory to predict the shape of NO. 16 marks 3 marks 1

Demonstrate how a Robinson annelation could be used to make the molecule below. Your answer should indicate all required reagents and include the mechanism for this reaction.

(b) In what way are these reagents different? Give an example of a reaction that could only be done using one of these two reagents (and clearly indicate which one).

(a) We discussed LiAlH4 and NaBH4 several times during problem sets. In what way are these reagents similar Give an example of a reaction that could be done using either reagent.

(a) Under what circumstances is it helpful (or even necessary) to use an auxiliary functional group? (b) Give an example of a reaction using an auxiliary functional group (in which it would have been necessary). (c) Demonstrate how to remove the auxiliary functional group you used in your answer to part (b).

Imipramine (Tofranil) has the structure shown below W A Where isare the best place(s) to disconnect between the two nitrogen atoms Explain your choice(s).

Aripiprazole (Abilify) has the structure shown below James cr H Which of the four main approaches to retrosynthesis would dominate your analysis of this molecule Justify your choice.

Fluoxetine hydrochloride (Prozac) has the structure shown below H Propose a synthesis of fluoxetine hydrochloride. 4(trifluoromethyl)phenol is commercially available (and affordable). You may use any other reactants and reagents that you could reasonably expect to be commercially available.

(a) There are hundreds (possibly thousands?) of ways to oxidize a secondary alcohol to a ketone. Give two examples of reaction conditions that can accomplish this. (b) Which of your two examples is greener? Explain.

We saw two different reactions involving ylides as reagents. (a) The Wittig reaction involved a phosphonium ylide reacting with a carbonyl. Draw both resonance structures of one example of a phosphonium ylide. (b) We also saw a reaction involving a sulfonium ylide reacting with a carbonyl. Draw both resonance structures of the sulfonium ylide. (c)

Diethylzinc (Et2Zn) is often used a source of nucleophilic carbon. (a) Would you expect this to be a hard nucleophile or a soft nucleophile? Explain. (b) Diethylzinc is pyrophoric (catches fire easily in the presence of water or air). Why?

In this course, we discussed three of the four main approaches influencing choice of bond-set. (The fourth approach was use synthetic methods in which you already have expertise.) (a) What is a bond-set? (b) What were the three approaches we discussed? Briefly describe each.

When an alcohol is reacted with an acid chloride, an amine such as pyridine is usually included as a nucleophilic catalyst. Propose a mechanism for the reaction below and explain how the inclusion of pyridine accelerates the reaction. i cr

LDA is made by reacting diisopropylamine with butyllithium. (a) Write a balanced chemical reaction for this reaction (including structures of all reactants and products). (b) Both LDA and butyllithium are strong bases. So, why would we ever want to make LDA instead of just using butyllithium

The biosynthesis of phloracetophenone is shown below. HH G SEnz SEnz HO OH OH phloracetophenone SEnz stands for a sulfur atom that is part of an enzyme. Explain what is going on in each step of this biosynthesis. You may use generic acids (HA) and bases (B) in any mechanism as it is reasonable to assume that there are enzymes present with both

Propose a synthesis of cinnamyl acetate (shown below). You may use any starting materials that you might reasonably expect to be commercially available as long as no single starting material contributes more than four carbon atoms or one benzene ring to the final product.

(a) Paraformaldehyde can be used to generate very pure formaldehyde for use in some biological labs. Heating paraformaldehyde gives formaldehyde gas in an equilibrium process. (i) Write a balanced chemical equation for the equilibrium between formaldehyde and paraformaldehyde. Instead of using the abbreviated form above, set n4 and draw the whole

Chemists tend to prefer 1,3,5trioxane over paraformaldehyde for practical reasons. As a polymer, paraformaldehyde is fairly insoluble in most solvents whereas 1,3,5trioxane dissolves in a variety of common organic solvents. Addition of a catalytic amount of acid to the solution is usually necessary. (i) Suggest a reasonable mechanism for the

Suggest a reasonable mechanism for each of the two reactions below, and explain the key difference(s) between them. .nl H3CO H3CS mb

(b) (i) Suggest a reasonable mechanism for step #2

(a) Consider the following sequence of reactions (i) Suggest a reasonable mechanism for step 1. Clearly indicate when experimental conditions change (i.e. when a new reagent is added). 4 marks

Why do carboxylic acid derivatives undergo substitution reactions while aldehydes and ketones undergo addition?

I Unknown X HC CC1 CH3,6. (a) (b) (d) The following page contains spectra for Unknown X (C6H6O4). 15 marks Identify Unknown X based on these spectra. Draw your answer in the box provided below. Use this page to explain your reasoning. On both NMR spectra, assign as many peaks as you can by numbering the peaks from left to right, drawing Unknown

3. (a) Consider the following molecule Br Br 8 marks If you were to analyze this molecule by mass spectrometry, what would you expect to see in the molecular ion region Your answer should address both the value(s) at which you would see peaks and the ratio of those peaks. 4 marks You do not need to explain your answer.,(b) Identify two fragments

Unknown X H H CH3,5. (a) (b) (d) The following page contains spectra for Unknown X (C8H100). 20 marks Identify Unknown X based on these spectra. Draw your answer in the box provided below. Use this page to explain your reasoning. On both NMR spectra, assign as many peaks as you can by numbering the peaks from left to right, drawing Unknown X in

A sample of Kr at a temperature of 80.80C was found to exert a pressure of 3.63 atm in a closed container with a fixed volume. FIND) What is the concentration, M, of Kr If the pressure was changed to 5.18 atm. What is the new concentration for Kr gas What is the density (gml) of Kr when exerting 5.18 atm (MW 83.8 gmole) The density of Kr at STP

Every radioactive element has a half life of billions of years True or False

Assuming equal concentrations, arrange these solutions by pH.

RbOH(aq) CaBr(aq) CH, NH, Br(aq) Na, S(aq) HBr(aq)

1. (a) In this question, relative order is important not absolute position. Incorrect lists that could be fixed by moving one molecule received 1 mark. Incorrect lists with either the first or last item correct received 0.5 mark. All other incorrect answers received 0 marks. Rank the following substrates in order from slowest E1 reaction rate to

Draw the organic product for each of the following reactions,(a) (b) H 3H OH HICH CH3 H C CH Swern oxidation 1. 2. EtN CI CrO3, H2SO4 HC CH,(c) H OH CH3 CH3 PCC, CHCl