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

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

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

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

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

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

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

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

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

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

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

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

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

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?

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

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. 3150-2850 cm-1 1720-1600 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.

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

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.

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