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Experiment 1: diels-alder and melting point

The purpose of this lab is to introduce the concept of the melting point of an organic compound as a first step in chemical identification of that compound and assessing its purity. In addition, you will synthesize a cyclic compound by employing the famous Diels-Alder Reaction.

Background information

Part 1: melting point

All solids display a characteristic melting point. With a pure substance, a melting point is the quickest and most accessible method for an organic chemist to confirm the identity of a compound (although in all fairness, NMR is the method of choice today because of its’ability to provide evidence of identity with concomitant additional information.).

Melting points can also be used to assess purity. You are all familiar with the concept of freezing point depression from Freshman Chemistry. Impurities in the solution prevent the ordering necessary to form a crystal lattice. This factor explains why salt/water solutions will not freeze until the temperature is as low as -20°C. The concepts involved with melting points are similar. In a perfect crystal, with no impurities, the melting point will occur at one temperature. However when impurities are introduced into the lattice, there is no longer a continuous crystal structure. Instead the solid is made up of different regions, some with more crystal imperfections then others. Not surprisingly the melting point will not be as sharp. This will also cause melting to begin earlier then expected. These impurities can even be water–Houston with high humidity!

It is a combination of these concepts that will be used in this lab. For the first part of the lab you will examine how adding an impurity will affect the melting point of the compound. In the second part of the lab you will determine the identity of an unknown by applying your knowledge of mixing properties that you gained in the first part of this experiment.

It will quickly become apparent that the melting points you measure will not match the melting points found in literature. You are encouraged, and it is to your advantage, to hypothesize why this is the case and to run your hypothesize by your TA to see if you are on the right track.

Find melting point data: For Part I you will be preparing mixtures of two compounds. Before lab you should look up the melting points of these two compounds. Possible sources can be Aldrich (Fondren location: TP202 .A42 2000-2001 REFERENCE-TRADE) or Acros chemical catalogs or online at (External Link) or (External Link) . These compounds are cinnamic acid and urea.

Part 2: diels-alder reaction

The Diels-Alder reaction is essentially a cycloaddition reaction (Cycloaddition reaction is one example of a special class of reactions called pericyclic reaction. Other examples of pericyclic reactions are electrocyclic reactions, sigmatropic reactions) in which an alkene adds to a 1,3-diene to form a 6-membered ring. The reaction is synthetically very useful, due to the formation of cyclic products. This is another Nobel-prize-winning reaction (1950) that provides flexibility to synthetic organic chemists. In this reaction a conjugated diene (this is one with alternating double and single bonds) is heated with a dieneophile - a compound with a multiple bond with an attached electron-withdrawing group (EWG).

Questions & Answers

How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
How can I make nanorobot?
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
how can I make nanorobot?
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
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Source:  OpenStax, Chem217labsfall07. OpenStax CNX. Oct 16, 2007 Download for free at http://cnx.org/content/col10463/1.4
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