1. Second week of a three-week experiment
Chemical Synthesis
Second week of a three-week experiment
Week 5
Today’s Agenda:
Review of chemical syntheses and yields.
Discussion of recrystallization
Performing recrystallization.
Determining melting point.
Determining unreacted salicylic acid
Thin layer chromatography (next week).

2. Chemical Synthesis: Review
In your groups, summarize what you accomplished last week.
Do you have dry aspirin? If so, how much? Do you have your % yields?

3. What’s next? Can we put our crude aspirin into tablets?
Let′s think!
What’s next? Can we put our crude aspirin into tablets?
What kind of chemical analysis is purification?
How are we going to achieve it?
The government will require purification and testing before we can market.
separation
precipitation

4. Recrystallizing Aspirin
Let′s think!
Recrystallizing Aspirin
In your groups review your responses to the following pre-lab question and come up with a consensus answer.
Using the Summary of Steps given in chapter 7 of the lab book as a guide prepare a set of directions for performing the recrystallization.  Make sure to include all the materials and equipment you expect to use. 

5. How can we know how effective our purification procedure is?
Let′s think!
Assessing purification
How can we know how effective our purification procedure is?
In your groups discuss how you would go about determining how effective your purification of your aspirin is.

6. Experiment Flow
If you have 0.4 g or more of aspirin, divide your aspirin in half and mass each portion. (If you don’t have 0.4 g, consult your TA)
Save half as crude product.
THIS WEEK
Determine melting point
NEXT WEEK
Perform TLC
RECRYSTALLIZE half and save as purified product.
THIS WEEK
Determine melting point
NEXT WEEK
Perform TLC

7. Chemical Synthesis Pre-lab
quiz questions
class results

8. Divide your product in half. Recrystallize half your aspirin product.
Let′s explore!
First Challenge
Divide your product in half.
Recrystallize half your aspirin product.
Available resources:
ethanol
glassware
ice bath
hot plate
Use your procedure as modified here in class.
You have 30 minutes

9. Now for the Qualitative Question.
How pure is your aspirin?
Your problem is to assess the purity of your aspirin with the intent of making the argument that it is pure enough to market.

10. What methods will you use to assess the purity of your aspirin?
melting point
TLC

11. Melting Point Determination
Let′s review!
In your groups answer the following
define melting point
define melting point range.
explain why it can be used to identify a substance.
explain how it can be used to determine the purity of a substance.
outline the steps required to obtain a melting point range using the Mel-temp.
Melting Point Determination

12. Safety precautions.
the melting point device can get very hot. Be careful to not burn yourself.
the thermometer must not be left in the melting point device once measurements have been made.

13. Capillary Tubes Two different ones:
Let′s review!
Capillary Tubes
Two different ones:
closed-ended tubes are for melting point which you will do today.
open ended tubes are for TLC which you will do next week.
do not mix them up!
& don’t forget – they’re GLASS WASTE!

14. Melting Point Challenge
Let′s explore!
Melting Point Challenge
Melting Point Determination
Available resources:
Melting point apparatus (one devices per group of four).
Your aspirin
When you have a melting point range for your product, report it

15. Thin Layer Chromatography This Challenge will be performed next week.
Let′s explore!
TLC Challenge
Thin Layer Chromatography
This Challenge will be performed next week.

16. Introduction From p. 65 of your Technique Book:
Introduction. A description of what is already known, the plan of action and expected outcomes.
From p. 71 of your Technique Book:
Introduction. A description of:
the experimental objective(s)
pertinent background information
expected outcomes, if any

17. Introduction: Helpful hints
Only include information that is known before lab. No results, observations, etc.
200 word maximum for one week lab.
Paragraph format. Subheadings okay.
Give items in context. No lists.
See Technique Book pp. 65, 67 and 71 for more help with writing an Introduction
See Technique Book pp for more help with scientific writing.

18. Thinking about the Report Discussion
Discuss your yield of aspirin. Is it a good yield? Defend your opinion.
How pure is your aspirin? Discuss whether or not your aspirin is pure enough to be consumed.
Can your yield be improved upon? How and where?
Things you will need to consider when you write your report.
Due in two weeks.