UCLA Organic Chemistry Thin Layer Chromatography Mandatory Technique Questions

TLC PRACTICAL: VERSION 16 QUESTIONS
1. You’re trying to isolate limonene, an oil found in grapefruits which can be used to make
medications. You will use TLC to determine if the compound you obtain is limonene.
To carry out the TLC, you will need to create a 2:3 hexanes:ethyl acetate eluting
solvent. If you want a final volume of 10 mL of solvent, what volumes of hexanes
and ethyl acetate would you need to add?
(A) 2 mL ethyl acetate and 8 mL hexanes
(B) 6 mL ethyl acetate and 4 mL hexanes
(C) 3 mL ethyl acetate and 6 mL hexanes
(D) 4 mL ethyl acetate and 6 mL hexane
2. Write out a procedure as a numbered list of the specific steps you should take for
TLC, assuming you are given a standard for limonene. Be specific enough with
your procedure that another student following it would be able to avoid mistakes.
Include directions for creating an eluting solvent, preparing your chamber and plate, and
how you would be able to tell whether your TLC experiment supports the claim that your
compound is limonene. Use the eluting solvent mixture from Q1.
3. A student sets up their TLC as shown in the image below, but there is a problem with this
setup. *** The issue IS NOT a missing piece of filter paper! ***
(a) Identify the problem and how the problem would affect the TLC plate after
elution.
(b) Use Chemix to diagram a corrected version. Make the spots blue. Use a
“tank” as the TLC chamber and an ellipse from the shapes menu as the lid.
_____________________________________________________________________________________________
POSTING COURSE MATERIALS VIOLATES UNIVERSITY POLICY
According to the UC Office of General Counsel and the University Committee on Educational Policy it is a violation of the
student code of conduct to post course materials on commercial web sites such as Course Hero, Koofers, and Chegg.
Students caught doing so are subject to a failing grade in the course
and disciplinary action by the University.
4. Use Chemix to depict the appearance of your TLC plate if the isolated oil is
limonene. The Rf value of your standard limonene is 0.6. Make your spots blue.
Make your TLC plate as short as possible in your depiction. Line up the ruler with the
side of your TLC plate, with the first tick mark at the spotting location.
5. Calculate Rf values of the compounds on the TLC plate below. Order the
compounds in Lanes 1-4 by increasing polarity (Lane 1 = leftmost lane w/ red
spot).
6. This is a TLC plate that has been eluted and taken out of the eluting chamber
Identify a significant problem that you see, explain why it is a problem, and
describe how the procedure should have been done differently to prevent it.
_____________________________________________________________________________________________
POSTING COURSE MATERIALS VIOLATES UNIVERSITY POLICY
According to the UC Office of General Counsel and the University Committee on Educational Policy it is a violation of the
student code of conduct to post course materials on commercial web sites such as Course Hero, Koofers, and Chegg.
Students caught doing so are subject to a failing grade in the course
and disciplinary action by the University.
Student ID here
Lab section code
Your Name Here
TLC Practical Version
#
Instructions for Using Template
1. Do NOT resize this document in any way. Do not change margins or page size.
2. ANY highlighted text in yellow in a box should be replaced with your relevant
information. This includes your name, the practical version, student ID, answers, etc.
3. Your answer for each question MUST fit inside the box given. DO NOT resize the box.
4. Failure to follow these instructions will result in no points given for that question.
5. You will convert this template into a PDF once you are ready to submit it.
Academic Honesty Statement
Copy the following academic honesty statement BY HAND (on paper or using note-taking
app). Sign it. Take a photo or screenshot and post it here.
I certify that: (a) the work presented is my own work, (b) I have not used any prohibited
external resources such as message boards or group chats, (c) I have not collaborated with
any other student, and (d) have followed all other rules pertaining to academic honesty for
Chem 51LB.
Signature _____________ Date ________
Q1
Include letter AND solvent
Example X. 4 mL benzonitrile and 6 mL acetone
Q2
Your answer for writing out the procedure goes here. Your answer must be written in Times
New Roman 12 pt. font. Your answer MAY NOT extend below this page.
Your answer for writing out the procedure goes here. Your answer must be written in Times
New Roman 12 pt. font. Your answer MAY NOT extend below this page.
Q3
Your explanation for the problem observed AND the new TLC plate from Chemix should be
here. Do NOT resize the box.
Your explanation for the problem observed AND the new TLC plate from Chemix should be
here. Do NOT resize the box.
Q4
Your TLC plate from Chemix goes here. Do NOT resize this box.
Q5
Your calculations of Rf value go here. You can do calculations in Word or Google Doc OR
you can do calculations by hand and insert a photo or screenshot.
Your polarity ranking also goes here!
Q6
Your answer and explanation for Question 6 goes here. Your answer must be written in Times
New Roman 12 pt. font. Do NOT resize this box.