1. Instructor: Renan Gongora CHM 2211L Spring 2017
Aspirin Synthesis
Instructor:
Renan Gongora
CHM 2211L
Spring 2017

2. Lab Report: Reaction Scheme
REACTANTS
PRODUCTS
CATALYSTS
TEMPERATURE
TIME
PERCENT YIELD
(PRESSURE IF NOT ATMOSPHERIC)

3. Aspirin Synthesis: Overview
Background/Mechanism
Experimental Setup
Two Questions
Infrared Spectroscopy
Background
What to expect
Disubstituted Benzenes
Get into pairs
Outline

4. Background acetyl group acetic anhydride salicylic acid
Notice the acetyl group and how each of the names that contain the prefix acet or acetyl contain the acetyl group in some way
Special one is the anhydride the anhydride functional group is flanked by two R groups but it implied that they are methyl if it is acetic like wise the carboxylic acid group
salicylic acid
acetylsalicylic acid
acetic acid

5. YOU WILL NOT BE TESTED ON THE MECHANISM
Nucleophilic attack
Proton Transfer
Proton Transfer
Single headed arrows vs. single headed arrows!

6. YOU WILL NOT BE TESTED ON THE MECHANISM
Proton Transfer
Loss of
Leaving Group
AcOH

7. YOU WILL NOT BE TESTED ON THE MECHANISM
Proton Transfer
acetylsalicylic acid

8. YOU WILL NOT BE TESTED ON THE MECHANISM
Nucleophilic attack
PNP PLP
Proton Transfer
Proton Transfer PT NA PT PT LG PT
Proton Transfer
PNP, PLP
Loss of
Leaving
Group
Proton Transfer

9. Procedure 5 mL and 5 drops of sulfuric acid Aspirin
precipitates out!!! WHY???
2 g

10. Procedure Weigh filter paper before this step What is in the flask?
H3O+

11. Aspirin Summary Synthesize Aspirin Purify Aspirin Weigh Aspirin
Salicylic acid, acetic anhydride and sulfuric acid (via reflux)
Purify Aspirin
Separating from other materials
Crystallize
Filtration
Weigh Aspirin
Preweigh the filter paper prior filtering
Let wet cake sit in vacuum setup (≈10mins)
Place wet cake in oven (keep an eye on it)
Analyze Aspirin
Spectroscopy (IR, 1H NMR)
Please read up on the theory of reflux!!!! You may be quized sometime in the future about reflux since you have already had an introduction on it

12. Aspirin Synthesis: Overview
Background/Mechanism
Experimental Setup
Two Questions
Infrared Spectroscopy
Background
What to expect
Disubstituted Benzenes
Get into pairs
Outline

13. IR Spectroscopy: How to Operate
spectra
(plural)
spectrum (singular)
Clean the sensor with isopropanol
Run the background scan
Add sample
Place arm over and pressurize to 60 units
Hit scan twice
Label important peaks
Pro tip:
Have an idea of what peaks you are looking for ahead of time

14. IR Spectroscopy: Energies in IR Region
Stretching: Fluctuating bond lengths
Bending: Fluctuating bond angles
Simple analogy: Hooke’s law
Atoms or groups connected by bonds can be thought of as masses attached by a spring
What does this help us identify?

15. IR Spectroscopy: Motivation
Rapid and simple method for functional group identification present in a sample
Does not elucidate carbon/hydrogen framework of the entire molecule

16. IR Spectroscopy: How it Works
De Broglie Equation (Light)
In an IR spectrometer, a sample is irradiated with frequencies of IR radiation, and the frequencies that pass through (that are not absorbed by the sample) are detected.
A plot is then constructed show- ing which frequencies were absorbed by the sample. The most commonly used type of spectrometer, called a Fourier transform (FT-IR) spectrometer, irradiates the sample with all frequencies simulta- neously and then utilizes a mathematical operation called a Fourier transform to determine which frequencies passed through the sample.
Several techniques are used for preparing a sample for IR spectroscopy.
The most common method involves the use of salt plates. These expensive plates are made from sodium chloride and are used because they are transparent to IR radiation.
If the compound under investigation is a liquid at room temperature, a drop of the sample is sandwiched in between two salt plates and is called a neat sample. If the compound is a solid at room temperature, it can be dissolved in a suitable solvent and placed in between two salt plates. Alternatively, insoluble compounds can be mixed with powdered KBr and then pressed into a thin, transparent film, called a KBr pellet. All of these sampling tech- niques are commonly used for IR spectroscopy.
cm-1
cm-1
A molecule may absorb light (photons at a specific frequency) that causes vibrations (stretching or bending) which ultimately lead to a peak on the spectrum.

17. Identification of Functional Groups with IR Spectroscopy
more rigid
less rigid
low mred
high mred

18. ATR-IR Spectroscopy
In an IR spectrometer, a sample is irradiated with frequencies of IR radiation, and the frequencies that pass through (that are not absorbed by the sample) are detected.

19. IR Spectrum: Starting Material
In an IR spectrometer, a sample is irradiated with frequencies of IR radiation, and the frequencies that pass through (that are not absorbed by the sample) are detected.
% transmittance
wavenumbers/ cm-1