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acs practice exam, Exercises of Chemistry

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Chem 360 Jasperse Final Exam Notes. Special Topics
1
Preview For ACS-Sandardized Final Exam
1. 70 Multiple Choice questions. Each has four possible answers.
2. Scoring is based on correct answers. If you don't know the answer, it pays to guess. I t
especially pays to rule out one or two obviously incorrect answers, even if you aren't sure about
which answer is actually correct.
3. Total time will be 2 hours (120 minutes). This means you have 1 minute and 43 seconds per
question. Time management is important, but most students complete in time. A more common
error than going too slow is to work too fast, hurrying early in the test and not taking enough
time to carefully read through the questions and look at all of the answers. I think it is foolish to
ever leave before time expires on a multiple choice exam, because the time wasted by leaving early
will usually be enough to have rechecked several guess problems and to have eliminated some
impossible answers. If time permits, you would like to answer the problem on your own, and
then see if your answer matches one of the listed alternatives.
4. Calculators are permitted, but there is only one problem that involves arithmetic, and you can
probably solve that one by hand.
5. Scores, Percentiles, and Grades
The statistical analysis is based on the performance of students from 64 colleges. Shown
below are some raw scores with the corresponding national percentiles and the grade that would
correspond.
Raw Percentile Grade Raw Percentile Grade
10 0 F 35 58 B
17 5 F 37 64 B
(17.5 should be the statistically average score 39 69 B
of a monkey guessing!) 43 78 B
20 10 D 44 80 A
21 12 D 45 81 A
23 18 D 50 89 A
24 21 C 55 95 A
26 28 C 60 98 A
29 38 C 65 100 A
30 41 B 70 100 A
31 45 B
33 52 B (this is average, slightly less
34 55 B than half of the answers!)
6. Problems are scattered from throughout the book. It is the intent of many of the problems to
try to integrate ideas from two or more different chapters. While most things are covered
representatively, it is imperative that you be well versed in the general principles of E1, E2, Sn1,
Sn2 reactions and of carbonyl compounds.
Nomenclature will be covered. Spectroscopy will be covered, but lightly (only about 3
problems, one H-NMR, one C-N MR, one IR.)
By my count there are about 45 problems that I would consider very straightforward,
comparable to problems you have seen before on tests, book homework, or quizes. There are
perhaps 20 problems that I would consider tricky but doable; there are maybe 5 problems that I
would consider very hard, and which may be almost totally unfamiliar to you.
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Preview For ACS-Sandardized Final Exam

1. 70 Multiple Choice questions. Each has four possible answers. 2. Scoring is based on correct answers. If you don't know the answer, it pays to guess. It

especially pays to rule out one or two obviously incorrect answers, even if you aren't sure about which answer is actually correct.

3. Total time will be 2 hours (120 minutes). This means you have 1 m question. Time management is important, but most students complete in time. A more commoninute and 43 seconds per

error than going too slow is to work too fast, hurrying early in the test and not taking enough time to carefully read through the questions and look at all of the answers. I think it is foolish to

ever leave before time expires on a multiple choice exam, because the time wasted by leaving early will usually be enough to have rechecked several guess problems and to have eliminated some

impos then see if your answer matches one of the listed alternatives.sible answers. If time permits, you would like to answer the problem on your own, and

4. Calculators are permitted, but there is only one problem that involves arithmetic, and you can probably solve that one by hand.

5. Scores, Percentiles, and Grades The statistical analysis is based on the performance of students from 64 colleges. Shown

below are some raw scores with the corresponding national percentiles and the grade that would correspond.

Raw 10 Percentile 0 Grade F Raw 35 Percentile 58 Grade B

17 (17.5 should be the statistically average score 5 F 3739 6469 BB

of a monkey guessing!) 2021 1012 DD 434445 788081 BAA

2324 1821 DC 5055 8995 AA

262930 283841 CCB 606570 98100100 AAA

3133 4552 BB (this is average, slightly less

34 55 B than half of the answers!)

6. Problems are scattered from throughout the book. It is the try to integrate ideas from two or more different chapters. intent of many of the problems to While most things are covered

representatively, it is imperative that you be well versed in the general principles of E1, E2, Sn1, Sn2 reactions and of carbonyl compounds.

problems, one H^ Nomenclature will be covered.-NMR, one C-NMR, one IR.)^ Spectroscopy will be covered, but lightly (only about 3

comparable to problems you ha^ By my count there are about 45 problems that I would consider very straightforward,ve seen before on tests, book homework, or quizes. There are

perhaps 20 problems that I would consider tricky but doable; there are maybe 5 problems that I would consider very hard, and which may be almost totally unfamiliar to you.

introduced throughout the year.^ In terms of subject^ distribution, questions are divided fairly equally between material Nevertheless many fall concepts have been used extensively in

spring. If you had total command of your 360 notes and problem sets, you could truly get 45 out of 70 right, I think. - 50

the notes if my time was limited.. I would probably do minimal studying from the text directly,^ Study strategy:^ Study hard, and it will pay off. I would probably work strictly from

but you would do very well to use the su To try as many book problems and/or practice tests as possible would help.mmary sections to help review many of the reactions.

practice tests?) early on, just so that yo^ How much should you study from 350?u know how much you remember and how much you^ I would go through all of your 350 notes (and

have forgotten. easy than it did originally. My expectation is that a large amount of the old material will now seem more The exception to this generalization is in the area of specific

reactions. reviewed before the test. Many of your reactions from fall have not been reused regularly, and will need to be

What will it Take to Get a Target Grade? A = 80th percentile B = 45th percentile C = 20th percentile D = 10th percentile

What will it Take to Get Certain 7  7 a C?

50/50 Guess Clueless 2043  1011

Total 70  28 = 35th percentile = C

What will it Take to Get a B? Comfortable B: What will it Take to Get an A? Comfortable A:

Certain 50/50 Guess 2020  2010 Certain50/50 Guess 3520  3510

Clueless Total 3070  737 = 64th percentile = B CluelessTotal 1570  449 = 88th = A

Summary: The above analysis suggests that if you know only 35 (half) for sure, you will get an A! If you know even 20 for sure, you can get a B! If you know even so much as 10

for sure, you are likely to get a C! totally guess on 15 problems and still get an A!), the key is that you get at least While you will not get them all right (a student can some of

them absolutely certain, and can make an educated guess on a reasonable portion of the rest.

Special Grade Incentive 90 th percentile  Special A Even if semester numbers wouldn’t justify

8070 thth^ percentilepercentile  Special BSpecial C Even if semester numbersEven if semester numbers wouldn wouldn’’t justifyt justify

Score and convert that back to a letter grade and it-Handling: I will take your raw score, use national norms to convert it to a percentile score,’s equivalent percentage on one of my normal 100-

point tests. I will then multiply that by 1.5 so that it ends up worth 150 points!

2. Alkyne Alkylations R C C H (Section 9.6,7. Representative Problems: 9.5R C C -8)

Ka = 10 -^23 S (BtruoLni,g L BDaAs,e NaNH 2 )

Electrophile R C C E

Overview • • Alkyne hydrogens are weakly acidic.They can be deprotonated by strong bases to generate carbanions.

  • Like other c and can react with electrophilesarbanions (Grignards, enolates….) the anions are strongly nucleophilic

Details • Acidity o The K

o o Why? Acidity follows hybridization: sp > spWhy? a^ value for acetylenes is about 10The more s character, the closer the electrons are gripped by the-^23 , (comparable to a ketone).^2 > sp^3

  • Base Requirements o positive nucleus. (Reverse of amine basicity…)Complete deprotonation is required:

o o o Therefore, strong bases are required.Oxygen anion bases (NaOH, NaOMe…) are too weak.Nitrogen bases are good: NaNH

  • 3 Electrophiles:^ o^ Carbon bases are good: BuLi^2 or LDA
    • • • Carbonyls (aldehydes and ketones, just as for Grignard and aldol reactions…)Alkyl halides (SN2 reactions)Epoxides Ph C C H^12 ..^ NaNH^2 Br

H

12 .. BacueLtione

  1. H+ H 3 C C C H^12 ..^ NaNH^2 O
  2. H+

3. Nucleophilic (Anionic) Aromatic Substi Representative Problems: 17.25a-d) tution for a Leaving Group : (Section 17.12A.

Cl W

W W Nucleophile^ Z^ Z W ANIONIC W^ W +^ Cl Substitution

  • Mechanism: Anionic analog to cationic aromatic substitution
  • Differences: o no ortho/para/meta issues. and the nucleophile must attack at that spot. A halide leaving group must be in the starting material,

o Reactivity depends on anion stabilizers at the ortho and para positions. have substitution, which benefit from electron donors…) one or more electron withdrawers present. (Unlike cationic You mustaromatic

o o The gets no resonance benefit.Meta withdrawers don’t help much. withdrawing groups must be ortho and/or para, not meta, otherwise the anionic

  • • Leaving groups: rate determining step,Nucleophiles: NaOH, NaOR, NH Cl, Br, I, even F (which halogen doesn’t matter much, because addition is not the elimination)

3 , RNH 2 , NaNHR (anion or nucleophilic amines)

Cl CH 3 CH 2 NH 2 (excess) NO 2

NaOCH 3 NO^2

Rank the reactivity of the following towards NaOH:Cl

NO 2

NO 2 Cl NO 2

NO 2 Cl NO 2

O 2 N^ Cl O 2 N NO 2

Cl

Common Question formats:^ A^ B^ C^ D^ E

A. What is product? C. following reaction? Which would be an intermediate or the resonance structure of an intermediate in the B. Rank reactivity (or, which is fastest? Or slowest?)

CH 3

CH 3

H^ H^ B Brr^ CH^3

CH 3

H^ Br^ H Br^ CH^3

CH 3

B^ Brr^ H H^ CH^3

CH 3

HBr B Hr^ CH^3

CH 3

B^ Crl^ H H^ CH^2 OH

CH 3

H^ H^ B Brr

A B^ C^ D^ E^ G

CH 3

CH 3

H H B Crl

F

1. Which of the above molecules are chiral?

2. Which of the above molecules are meso compounds?

3. Classify the relationship between the following pairs as same, enantiomers, or diastereomers:

  • A + B
  • A + C
  • B + D
  • E + F

4. Classify the R/S stereochemistry for the chiral centers in A and B.

5. Polymers Representative Problems: 26.22 (isobutylene is 2: (Section 8 - 16, 26 - 2 [addition polymers],-methyl - 271 - -propene), 26.23, 26.27) 7 [condensation polymers]..

Addition P • No change in atoms, you simply add all the atoms in the reactants together to make long polymer strings. The repeat unit in the polymer must have the same atoms as the monomer. olymers

  • • • Precursors: Alkenes or Conjugated DienesPolymer has one fewer doubFor a conjugated diene, the two middle carbons end up doublele bond than monomer: monoalkene-bonded in the polymer  none; diene  one.
  • • • Initiation/recognition: Usually radical/peroxides. Sometimes acid or Lewis acid catalyzed.Skills: Given monomeSkills: Given polymer, recognize monomer.r, draw polymer
  • Ex: Skills: Use and understand shorthand styrePnhe^ p^ heeraot^ xide etc^ H^ C^2 CPHh^ H^ C^2 C PHh^ H^ C^2 CPHh^ H^ C^2 C PHh^ H^ C^2 C PHh^ etc^ P sho^ ColHyrst^2 htCyarHnedPneh Cl p^ heeraotx^ ide C H 2 H^ C^ C Cl^ H^ C^2 C H 2 H^ C^ C Cl^ H^ C^2 C^ H 2 H^ C^ C Cl^ H^ C^2 etc^ "PCBD" (^2) b-ucthaldoireone

etc (^) CH s (^2) hCoHrt=hCaCndlCH 2

Problems: Draw the monomer and the shorthand version of polymerperoxide

monomer^ heat^ etc^ H^ C^2 CCHH^3 H^ C^2 C^ CHH^3 H^ C^2 CCHH^3 H^ C^2 C^ CHH^3 H^ C^2 C^ CHH^3 etc shorthand p heeraotx ide etc C H 2 C (^) C Ph^ H C (^2) C H 2 C C Ph^ H C^2 C H 2 C C Ph^ H C (^2) etc shorthand

Cl Cl Cl monomer

Draw the polymer from the following monomer, both shorthand and longstretch

"propyCleHn^3 e" CO 2 Me