week9 Problem Set

In fairness to the whole class, I will not discuss during my office hours what will be covered on the exam or what you should expect to be on the exam or any other probing questions that would give an individual an unfair advantage over his fellow classmates. If you have a question, submit it by June 1 so that I can post the answer for all to see.

Answers to Submitted Questions regarding the final exam

Question:

Date Submitted: Tue Jun 1 23:59:16 US/Pacific 1999

Student Name: mei

Dear Dr. Mouser, I am having a hard time with IR identifications like the one that you have for #11 on the Spring 99 exam..specifically the part where you ask for us to specify which type of stretches the peaks are. Do you expect to know how to identify asymmetric and symmetric stretches and specific bends? thanks

Answer:

(Spring 99?) Yes.

Question:

Date Submitted: Mon May 31 20:16:01 US/Pacific 1999

Student Name: me

prof- what's ligroin? how are we supposed to know about its properties- like polarity, etc...? how do you do p91 #5?--its on the fall 98 exam. oh, and do you have extra oh's this week or just the norm? what are your ohs? thanx professor!

Answer:

I answered this question in lecture. In brief, it consist mostly of mixed hexanes (i.e., n-hexane, 2-methylpentane, etc.) and mixed pentanes. I answered question #5 below. I will have no additional office hours. My hours are Tu/Th 12-1.

Question:

Date Submitted: Mon May 31 19:51:12 US/Pacific 1999

Student Name: ?????

Dear Professor Mouser, Would we need to memorize the IR numbers and the ones for NMR as well. DO we need to know both the Carbon and proton NMR????

Answer:

Answered these questions already. See below.

Question:

Date Submitted: Mon May 31 19:48:49 US/Pacific 1999

Student Name: Student

Dear Dr. Mouser, I have a question on #4 from the Dec 7, 1998 Practice CHem 130Al FInal. FOr number 4c and 4d, please explain howto do the problems 4c) Assuming compound Y as a 5% contaminant in X (on a mole-per-mole basis), what is the theoretical melting point range of compound X 4d) Assuming compound X is the expected product and compound Y is an impurity, if a sharp melting point is observed could it be certain that compound X is nearly pure (circle) and how please explain why the answer is yes or no. HOw do you do #5 on the same exam.... the question is : Benzoic acid is refluxed in excess ethanol in the presence of concentrated H2S04 (catalysis) until equilibruim is reacched (refer to the below equation)OUrline a separation scheme for the isolation of dry ethyl benzoate (use any needed solvent and reagents). NOte that ethyl benzoate is a liquid. (I did not understand the answer that was given.) Please help. THanks!!

Answer:

4c) draw a vertical line at 95% X. It will intersect two Curved lines. At these intersections, draw horizontal lines to the y-axis (temperature). From that you should get a mp range of 130-144. 4d) Yes, a sharp mp is observed at 158°C. [full credit was also give if one answered "No" with the explanation, "because it could be at the Eutectic point which also has a sharp mp".] 5) This was a hard question. Few got it fully correct. It's the techniques you don't understand? These are techniques we used in lab to isolate products. Depending on what you are trying to isolate (e.g., solid or liquid) will dictate which techniques you use.

Question:

Date Submitted: Mon May 31 17:06:09 US/Pacific 1999

Student Name: Mar

Hello. You mentioned in one of the answers you gave last yrs o-chem class 75 min for the final. If given a time limit least than 1hr and 50min could we request to work on the exam for the full 1hr and 50min?

Answer:

No.

Question:

Date Submitted: Mon May 31 16:31:47 US/Pacific 1999

Student Name: Jessica

Student Email: jeslange@ucla.edu

Submitted from: s246-82.resnet.ucla.edu

Dear Professor Mouser, I have 2 questions regarding the final. First, the exam from Fall 1998 that is provided in the lab manual contains a question that wants us to supply a carbon-NMR ourselves...Is there a chance that a question like this could come up on our exam? My second question is regarding exo-endo isomers...Do the secondary MO interactions always rule out over steric factors in determining which of the two isomers will be the major product? For example, if those secondary interactions exist for one of the isomers, do we just always assume that that product will be the major one? Thanks for your help.

Answer:

1. Question 14c would not be asked. This question ask you to draw a carbon-13 proton COUPLED spectrum. We never did this in lecture (we only covered carbon-13 proton DECOUPLED). 2. Secondary MO interactions do NOT always rule over steric effects. Note: in lab we were given the result and then tried to explain it using MO theory (and not the other way around).

Question:

Date Submitted: Fri May 28 22:12:30 US/Pacific 1999
Student Name: Biana Roykh

Hi Professor, This pertains to the Final. I was wondering if we are allowed to bring any note cards, or lab notebooks to the test, or is it all closed notes? Thanks.

Answer:

The exams is closed notes. No note cards. No Lab notebooks.

Question:

Date Submitted: Fri May 28 15:58:02 US/Pacific 1999

Student Name: student

For the synthesis of an ester experiment, the number I obtained by looking through the eyepiece of the machine is close to 1.40. What does this number mean? And how do I calculate the index of refraction of the ester? Thanks.

Answer:

That number is the refractive index for your compound.

Question:

Date Submitted: Thu May 27 18:26:09 US/Pacific 1999

Student Name: Lisa

Professor mouser, How long will the final be? Thanks. Lisa

Answer:

Assume 1 hour and 50 minutes. However, I will announce at the start of the exam how much time you will have. For last quarter's exam I gave the students 75 minutes.

Question:

Date Submitted: Wed May 26 16:06:13

Student Name: Diana Chang

Dear Dr. Mouser, Would the final be graded on a curve? And are we going to have a REVIEW Session from you for the FINAL EXAM? Thanks!

Answer:

On the final exam the top 12% of the class will receive an A. 13-18%, A-. The average score will be a C+. In reference to course grades: ~20-25% A's, 40-50% B's. Additional information: Grade distributions in lab sections will be the same with only one exception. If a lab section's final exam average is higher than the overall class average then there is a good chance that the Distribution of A's and B's will be higher for that section. There will be no review session.

Question:

Hi Dr. Mouser, I was wonderiing if you had to know proton nmr for the final, and will we have to memorize all the peaks on the carbon nmr or will they be given to us. What is the format of the final?

Proton NMR will NOT be on the final. See prior questions. See the example exam at the end of the 130AL course reader.

1. Will questions on the test come directly from the lab work, that is, will they have to do with the experiments we did in lab? 2. What charts will be provided on the test? 3. Is there any material that will not be covered on the test, or what will be covered?

1. The questions may be indirectly related to the lab. E.g., though we did the dehydration of cyclohexanol, I may expect you to determine the dehydration product of a different alcohol. 2. NMR table, IR table and the DEPT logic table will be given. 3. Only that material that I crossed out during lecture will not be covered.

Professor Mouser, Will we be able to use any notes on the final? Please reply soon. thanks. Lisa

hi prof mouser, what IR and Nmr data (positions on the scale) must we memorize? My ta gave us a lot of info and there are also a lot of #s in the reader. which are we expected to know? thanks

I will supply you with a copy of the IR table and NMR table at my home page at: http://www2.chem.ucla.edu/~mouser/General/labzone/130AL/130AL.html