Homework answers / question archive / End-of-semester Study Guide -- Chem 232 -- Spring 2021 -- Professor Doug Grotjahn This is a guide to concepts you should know at the end of this class

End-of-semester Study Guide -- Chem 232 -- Spring 2021 -- Professor Doug Grotjahn This is a guide to concepts you should know at the end of this class

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End-of-semester Study Guide -- Chem 232 -- Spring 2021 -- Professor Doug Grotjahn This is a guide to concepts you should know at the end of this class. Use this list in addition to problems in the textbook, the midterms and the practice midterms. All of the practice midterms, their answers, and the midterm answers are on Canvas. Coverage of the class is through the end of Chapter 12 of the book. Also, use the Concept Maps and Summary and Review tools at the ends of the chapters. Valence, valence electrons Bonds--polar, non-polar, covalent, ionic Hydrogen bonding Electronegativity Partial charges Formal charges Bond angles Bond lengths Dipoles Resonance structures Correct Lewis structures How many atoms and how many electrons? π and σ bonds Hybridization and changes in geometry and bond lengths, electronegativity Identifying functional groups Comparing structures: same or different bond pattern, same or different stereoisomer, diastereomers, enantiomers, meso compounds, conformers, constitutional isomers Fischer and Newman projections Chair forms of cyclohexane, axial and equatorial groups Acidity and basicity--ranking sets of molecules using structures or pKa information Acids, bases, conjugate acids and bases Position of acid-base equilibria Lewis acidity, Brønsted-Lowry acidity Memorize pKas of water, hydronium ion, ammonium ion, ethane, acetic acid, hydrogen chloride Arrow-pushing to show flow of electrons and changes in bonding Chirality--identify stereogenic carbons, determining R and S absolute configurations, drawing R and S configurations cis and trans and E and Z isomers Inversion and retention of configuration R and S Optical activity Identify changes in oxidation state of carbon Primary, secondary, and tertiary alcohols, alkyl halides, carbocations, radicals, alkyl groups, etc. Common names and structures: tert-butyl and iso-propyl groups Different stabilities of various alkenes, radicals, carbocations, and why there are differences Reactions of the various functional groups (very important--lots of material here) Mechanisms!! Focus on the few atoms and electrons which are shifting and how those changes move other nearby atoms or functional groups Markovnikov and anti-Markovnikov additions Using reactions to synthesize new organic molecules – including retrosynthetic analysis Naming organic compounds and functional groups Radical reactions Strength of bonds and their reactivity Primary, secondary, tertiary alkyl halides and how they react in SN1, SN2, E1, E2 reactions NMR (proton and carbon), IR, mass spectrometry Be able to predict spectra (e.g. diastereotopic protons, chemical shifts, splittings) and identify organic compounds using NMR, IR and mass spec data. Redox chemistry (half reactions) involving carbonyl compounds/alcohols. Final exam – Chem 232 – Spring 2021 1 1. (30 points) Predict the organic product(s). If more than one stereoisomer will form, be sure to show the possible stereoisomers. Be sure to indicate the stereochemistry if necessary and include all stereoisomers. If no reaction would occur, write "no reaction." (a) NaBH 4 H2O O OCH(CH3)2 (b) HI, heat O CH3 (c) CH3MgBr (excess), O O O (d) 1. BD3-THF 2. NaOH, H2O2 (e) OH PBr3 (f) 1. LiAlH 4, ether O 2. H2O, acid NH4Cl, H2O Final exam – Chem 232 – Spring 2021 2 (g) O OH TsCl, pyridine H3C O Na DMF please show intermediate (h) KMnO4, KOH, heat (note: show the product(s) before any acid is added – no acid is added) (i) (1) DMSO, (COCl) 2, CH 2Cl2 (2) Et3N H C OH CH 3 (j) Ni2B (P-2) + H2 (i) Br KOtBu, tBuOH Final exam – Chem 232 – Spring 2021 3 2. (18 points) For each of the following acid-base reactions, in the boxes provided, 1. Draw the products. 2. Identify acid, base, conjugate acid and conjugate base. 3. Predict whether equilibria will lie on the side or products or reactants. 4. Calculate Keq for each reaction as 10 to some power. For compounds whose pKas you were not asked to memorize, pick the most closely related compound of the six whose pKas you were asked to memorize, and assume that the unknown pKa is equal to the memorized pKa. As an example: you know the pKa of H3O+, which would be a good model for the related organic ion CH3OH2+; so assume the pKa of the latter equals that of H3O+. There are a couple of additional pKas you may or may not need; here they are: NH3, 38; H2, 35, terminal alkyne 25. Completed equation - write roles of acid, etc. below the formulae (a) H H O + (b) (c) H CH3 H HO + CH3Li (a) H O NaH + HCl H3C C C H + NaH (b) H HO H CH3 + HCl (c) CH3Li + H3C C C H H Equilibrium lies on side of….. Keq = Final exam – Chem 232 – Spring 2021 4 3. (8 points) Dimethyldioxirane (DMDO) can be used to convert alkenes into epoxides (oxiranes). Draw the mechanism of the epoxidation reaction of (Z)-but-2-ene with DMDO. CH3 C O CH3 DMDO Write the balanced chemical equation for the reaction. O 4. (10 points) Use correct Lewis structures, formal charges, and arrow-pushing for full credit. Ionic compounds should be clearly drawn as ionic compounds. (a) Draw the acid-base reaction between LiH and AlH3. What type of acid-base reaction is this? (b) Draw the Brønsted-Lowry acid-base reaction between water and this carbocation: H. 6. (10 points) Polyphenols have been shown to have important health benefits. We can talk more about polyphenol structure in Chem 432, but at the right I show part of the structure of polyphenols. #2 OH #1 #3 OH HO Note that there are three OH groups, #1, #2, and #3. They are not all equally strong Brønsted-Lowry acids. By drawing and showing the most important resonance structures, and using Cl- > Br- > I- Substitution vs. Elimination: SN1, SN2, E1, E2 Chem 232 -- Spring 2021 -- Professor Douglas Grotjahn (with thanks to Prof. Patrick Walsh) the carbon the carbon Substrate Is there a good leaving group? H yes C the leaving group X Substrate Moderate nucleophiles secondary tertiary I-, Br-, N3HS-, RS- -C N HO-, RO- , R2NPR - C C R 3 What is substitution pattern of the carbon? primary Is Nu a hindered and strong base? (3o alkoxide = hindered) Good/strong nucleophiles None of this applies...unless you can turn a poor leaving group into a good one! no + Nu C The nucleophiles (Nu) Nucleophiles in bold are strong bases ClO RSH, R2S R3N, R2NH, - C O R RNH2, NH3 Poor/weak nucleophiles FH2O, ROH O HO Is there a strong base present? C R Is Nu a strong base? (e.g. alkoxide RO-) no yes no Mostly alkene formation by E2 mechanism, some SN2 Is Nu a good nucleophile? yes Rapid SN2 reaction If Nu: = strong base, some E2 also no Slower SN2 Alkene formation (look at the C-H) by E2 in nonpolar solvent, E1 or E2 in polar solvent Note: higher temp. usually increases proportion of elim. over subst. yes no yes Is Nu a good or moderate nucleophile? Is the solvent polar? yes yes Rapid SN1 reaction, with some E1 if Nu is poor/weak no (Mostly) alkene formation (look at the C-H) by E2 mechanism; + SN2 Slow reaction SN2 reaction yes Substitution by SN1 no Is the solvent polar? no Slow reaction 452 CHAPTER 10 RADICAL REACTIONS Note: the scan is B+W but the "red" bonds can be identified by the long dashes e.g. some are highlighted in yellow at upper right ------ TABLE 10.1 SINGLE-BOND HOMOLYTIC DISSOCIATION ENERGIES (DH 0) AT 25 °C9 Bond Broken (shown in red) H-H D-D F-F Cl-Cl Br-Br 1-1 H-F H-CI H-Br H-1 CH3 -H CH3-F CH3-CI CH3 -Br CH3 -I CH3-OH CH3 -OCH3 CH3CH2 -H CH3CH2 -F CHsCH2 -CI CH3?H2 -Br CHsCH2 -I CHaCH2 -OH kJ mor 1 436 CH3CH2 -OCHs 443 CHsCH2CH2 -H 159 CH3CH2CH2 --F 243 CHsCH2CHr-CI 193 CH3CH2CH2 -Br 151 CH3CH2CH2 --I 570 432 366 41 3 439 355 298 (CH3bCH-OCH3 (CHsbCHCH2 -H (CHsbC-H 227 (CH3)sC-OH (CH3)sC-0CH 3 . from the ? ata compiled National Institute of Stan C6H5CH2 H 359 422 292 (CHshC-1 295 233 402 349 (CH3)sC-Br 353 222 400 (CH3)sC-CI 444 239 HC=C-H 400 369 465 378 CHs-CHa CHsCH2-CHa CH3CH2 -CH2CH3 (CH3hCH-OH 348 421 294 kJ mo1-1 474 547 C6H 5-H 355 (CH3hCH-l 387 354 CH2 = CH-H CH3CH2CH2 -OCH3 (CH3hCH-Br 352 293 240 423 444 CH2 = CHCH2-H CH3CH2CH2 -CH3 (CH3hCH-CI 461 352 Bond Broken (shown in red) 395 (CH3hCH- F 440 kJ mor 1 CH3CH2CH2 --OH (CHshCH -H 298 393 Bond Broken (shown in red) 371 374 343 (CHahCH-CHa 371 (CHa)aC-CHa 363 499 HO-H HOO-H HO -O H (CHa)aCO-OC(CH )a 3 0 II CaHs 0 II CO-OCC6H5 CHaCH2O-0CH 3 CHaCH2 O-H 0 356 214 157 139 184 431 II CHaC-H 348 3? dards (NIST) Stand ard Reference We?Book {http·//wehbook njsr.gov/chem Databas e Nu isrry /) op right 200 C m b r 69 David R., ed. DH0 values were obtained directly or cai l . ?ata from CRC Handbook fi O ? • July 2001 Release, Accessed via NIST Ch? cu ated rom eat of of Ch ust ry and form ation (H Physics, Updated 3rd lectronic Edition; ) i d at a usin ?; e E _ ? BJ. g quatio n DH0 [A _ B] = 11/[A.] + Hi [B.] _ Hj[/. These reactions rese b m le each oth (propane), and er in two re kaJle they b0th pr spe ts o d ? : they both begin with the saIJle al uc however' in the amonn e a n al .1;flt' kyl ra d lc::il ?nrt ? L __ .J t- ,...c --'T'heY OJ I TIME REMAINING: 2 DAYS, 12:11:21 Chem 232 final exam study help chemking 1 Day 3 Days 6 $80.00 Edit O Make Priva ?? ing on a chemistry test / quiz prep and need support to help me understand better. m reaching out to you directly as I am not sure how this works provide: high quality help, quick responsive communication, 3 original explanations and answers with a esources cited. ENTS Question 1 10 pts Match the indicated functional groups to their names. 1 ??. FO H ? 7 Br. FO 6 ON OCH3 12 HO CEN 10 1 [Choose 2 Choose ] > 3 [Choose ] < 4 [Choose ] > 5 [Choose ] > 6 [Choose 7 [Choose ] 8 [ Choose ] 9 [Choose > 10 [Choose V 11 [Choose ] 12 [Choose ] Question 1 10 pts Match the indicated functional groups to their names. 1 HO (mo O= H Br 6 O2N. OCH3 12 8 HO CEN 10 1 2 ? [ Choose ] Alkyne Carboxylic Acid Phenol Oxocarbon Aldehyde Ketone Benzene Ether Vinyl Bromide Nitro Alkyl Bromide Alkene Alkane Amide Ester Nitrile Amine 4 5 6 7 [Choose ] 8 [Choose ] v [Choose ] 10 [Choose V 11 [Choose ] < 12 [Choose ] < u Question 2 2 pts Give the correct pKa value for water, which I asked you early in the semester to memorize. Question 3 2 pts Give the correct pk, value for ethane, which I asked you early in the semester to memorize. U Question 4 2 pts Give the correct pKa value for acetic acid, which I asked you early in the semester to memorize. Question 5 2 pts Give the correct pK, value for ammonium ion, which I asked you early in the semester to memorize. Question 6 10 pts Rank the below compounds in order of their acidity. ( 1 will be the least acidic, 7 will be the most acidic ) A OH E B OH CI OH D OH 1 [Choose ] 2 [Choose ] > 3 [Choose ] 4 [Choose ] < 5 [Choose ] v 6 [Choose ] 7 [Choose] VueSLIUI ? opus Rank the following from highest to lowest boiling point (1=Highest, 5=lowest): 1 [Choose] 2 Choose] 3 [Choose ] < 4 [Choose ] v | Choose [Choose ] v Question 8 8 pts Below is the structure of Palmyramide A, a natural product isolated from cyanobacteria found near the Palmyra Atoll in the Pacific Ocean. Determine R and S for its stereocenters. HN ? A Select] D Select] B [Select] E Select ] [ Select ] F [Select ] Question 9 8 pts Match these substitution reactions to the correct mechanism: NaF 1) DMSO NaN 2) Acetone CI 3) CH3OH H0 EtONa CI 4) EtOH H 5) Br HO IN 1) [ Choose ] SN1 SN2 2) [Choose] 3) [Choose) v 4) [Choose ] 5) [Choose ] > Question 10 8 pts Match the following molecules with the correct relationship: A CI Br D CI. CI Br i NH NH2 B m HO HS OH CI CI OH HS Ho die boere C Br Br Br Br Br Br [ Select ] Enantiomer Diastereomer Identical Molecule Constitutional Isomer Resonance Structure JCICEL D: [Select E: [Select) F: [Select) > Question 11 8 pts Over and over again in class I ask, "how many atoms and electrons are directly involved in the bond- making and bond-breaking of the reaction?" For the following reactions, answer this question by filling in the blanks. PLEASE WRITE NUMERALS (1, 2, 3, etc.) not words, for credit. The mechanistic step in which bromide ion reacts with CH3OTs directly involves atoms and electrons. The mechanistic step in which CH3Br reacts with enough Li to make CH3Li directly involves atoms and electrons. Deprotonation of a carbocation at a beta-CH with a base directly involves atoms and electrons. A propagation step involving CH3 and Cl2 directly involves atoms and electrons. E2 elimination directly involves atoms and electrons. Alkyne Carboxylic Acid Phenol Oxocarbon Aldehyde Ketone Benzene Ether Vinyl Bromide Nitro Alkyl Bromide Alkene Alkane Amide Ester Nitrile Amine Alkyne Carboxylic Acid Phenol Oxocarbon Aldehyde Ketone Benzene Ether Vinyl Bromide Nitro Alkyl Bromide Alkene Alkane Amide Ester Nitrile Amine Question 11 8 pts Over and over again in class I ask, “how many atoms and electrons are directly involved in the bond- making and bond-breaking of the reaction?" For the following reactions, answer this question by filling in the blanks. PLEASE WRITE NUMERALS (1, 2, 3, etc.) not words, for credit. The mechanistic step in which bromide ion reacts with CH3OTs directly involves 3 atoms and 3 electrons. The mechanistic step in which CH3Br reacts with enough Li to make CH3Li directly involves 3 atoms and 3 electrons. Deprotonation of a carbocation at a beta-CH with a base directly involves 3 atoms and 3 electrons. A propagation step involving CH3 and Cl2 directly involves 3 atoms and 3 electrons. E2 elimination directly involves 3 atoms and 3 electrons. Question 11 8 pts Over and over again in class I ask, “how many atoms and electrons are directly involved in the bond- making and bond-breaking of the reaction?" For the following reactions, answer this question by filling in the blanks. PLEASE WRITE NUMERALS (1, 2, 3, etc.) not words, for credit. The mechanistic step in which bromide ion reacts with CH3OTs directly involves 3 atoms and 3 electrons. The mechanistic step in which CH3Br reacts with enough Li to make CH3Li directly involves 3 atoms and 3 electrons. Deprotonation of a carbocation at a beta-CH with a base directly involves 3 atoms and 3 electrons. A propagation step involving CH3 and Cl2 directly involves 3 atoms and 3 electrons. E2 elimination directly involves 3 atoms and 3 electrons.