DOC PREVIEW
UK CHE 230 - CHE 230 - Exam 2

This preview shows page 1-2 out of 5 pages.

Save
View full document
View full document
Premium Document
Do you want full access? Go Premium and unlock all 5 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 5 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 5 pages.
Access to all documents
Download any document
Ad free experience

Unformatted text preview:

Organic Chemistry CHE230-001 EXAM 2 KEY Page 1 of 4 Name: ______________________ Student ID No:____________ First: You are allowed to have a writing utensil, a calculator and molecular model set at your seat. Please put away all other materials. Second: Place your student identification on your desk. A proctor will come around to check everyone’s ID. Is your name and number on your test? Third: Quickly read through the entire exam. Your goal, as always, is to score as many points as possible. Do not waste time on problems that you can’t do if there are easy questions to do first. Fourth: It is critically important that your answers be written in a clear, unambiguous manner. Answers in which your intentions are unclear will not receive credit. SHOW YOUR WORK! Fifth: READ THE INSTRUCTIONS FOR EACH PROBLEM. answer each question Problem Number Points possible Score 1a. 14 _____ 1b. 10 _____ 1c. 10 _____ 1d. 08 _____ 2. 10 _____ 3. 08 _____ 4. 30 _____ 5. 10 _____ Total 100 _____Organic Chemistry CHE230-001 EXAM 2 KEY Page 2 of 4 1. (a) (14 pts for all otherwise two points each) Label the carbon atoms according to absolute configuration R, S or NA for not applicable in the case of non-stereogenic atoms. Remember that the convention is that the lower portion of the ring is closest to you. 1. (b) (10 pts) Glucose above is broken down by the body to yield CO2, H2O and energy. Use what you know about the chirality of our biochemistries and the nature of diastereomers and enantiomers to explain (short answer) the following question. Could we ingest the enantiomer of glucose and feel just as energetic? _No way, The enantiomer of glucose would be a diastereomer of glucose in the chiral _ __environment of the human body as such they would be different._________________ 1. (c) (10 pts) Living systems put glucose into other forms for specific purposes. The molecules are 1A: glucopyranose α-anomer, 1B: glucopyranose β-anomer and 1C: glucofuranose. Use what you know about ring strain and the conformation of substituted cycloalkanes to say which molecule is most stable and why and which molecule is least stable and why. Most stable:__1B___Why?_All groups are equatorial in a six membered ring__________ __________________________________________________________________________ Least stable:__1C__Why?__Five-membered ring means more strain. ___________________ __________________________________________________________________________ 1. (d) (8 pts) Pick the best word from following choices to complete the sentences below. *. Molecules 1A and 1B are ___diastereomers, one stereogenic carbon atom inverted___. Molecules 1A and 1C are __ structural isomers, same elements, different connections between them __. OOHHOHOHOHOOOHHOHOHOHOOOHHOHOHOHOOHOHHOHOHOOH1A 1B 1CSS R S R NAOrganic Chemistry CHE230-001 EXAM 2 KEY Page 3 of 4 2. (10 pts) When alkanes burn H2O and CO2 are produced. The heat of formation (∆Hf) for the following molecules are listed in kcal/mol. ∆Hf hexane: -39.9. ∆Hf heptane: -44.8 ∆Hf octane: -49.8. ∆Hf nonane: -54.5. ∆Hf cyclohexane: -29.4. ∆Hf cyclodecane: -58.8. Compute the ring strain in cyclohexene answer: _______~0 kcal/mole______ and the ring strain in cyclodecane answer: _____~9.8 kcal/mole ____ Show your work below. Hint, get the average increment for a –CH2– group. Use back of this sheet if you need more room. Approx. 4.9 kcal/mole(CH2) Strain in cyclohexene = -4.9*6-(-29.4) = 0 Strain in cyclodecane = -4.9*10-(-58.8) = 9.8 HRxn Coordinate∆-49.09.8 strain-58.8kcalvalue fora ten unstrained-CH2-Organic Chemistry CHE230-001 EXAM 2 KEY Page 4 of 4 Draw the product of 4B for 10pts extra. Is it the lowest-energy stereoisomer? 3. (8 pts.) Rank the molecules below by how fast they undergo E2 reaction mechanism. BrBrBrBrBrBr3A 3B 3C 3D 3EBrHHOnly the antiperiplanar H Br undergoesE2. So we need Br in the axial position to do antieliminationBrBr3DBrNot much axial Br stuffis in the equilibrium mixdue to high energy.Br3E3BBr3E does not have an antiperiplanarH to eliminate! FASTEST _D_ _C_ _A_B_E__ SLOWEST 4. (30 pts) Label the following reactions E1, E2, SN1 or SN2. Make little notes reflecting your thought process by each answer for possible partial credit if you are unsure of your answer. A. _E2_ B. _SN2_ C. _E1_Organic Chemistry CHE230-001 EXAM 2 KEY Page 5 of 4 5. (a) (5 pts) Do you expect 5A and 5B to react at the same rate under the given conditions? Why or Why not? ____No they are diastereomers______ (b) (5 pts) Do you expect 5A and 5B to give the same products under the given conditions? Why or Why not? ____Yes, two enantiomeric carbocations are produced. These can both eliminate to the same Saytzeff product. __________ ____No, if substitution, the reaction will produce diastereomers. The product mixture of 5A will be enantiomers of the product mixture of the other 5B. You know what is going on. The proton sits on the oxygen atom of the OH group making it a better leaving group then the rest is history. Please think about this one; it might help to write out the mechanism and draw out the reaction energy diagram. HOHOH2O/ H3Oproducts5A5BOSOOonly productmysteryreagentsBrNOsolventCNa+(strong unhinderednucleophile)OHH3O+/


View Full Document

UK CHE 230 - CHE 230 - Exam 2

Documents in this Course
Exam 3

Exam 3

5 pages

Exam

Exam

9 pages

Exam

Exam

5 pages

Exam

Exam

5 pages

Exam

Exam

5 pages

Exam

Exam

10 pages

Exam

Exam

10 pages

Load more
Download CHE 230 - Exam 2
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view CHE 230 - Exam 2 and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view CHE 230 - Exam 2 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?