In addition, you will synthesize a cyclic compound by employing the famous Diels-Alder Reaction.
The Diels-Alder reaction is stereospecific with respect to both the diene and the dienophile. Under the reaction conditions, the product can be broken down to its starting materials known as retro Diels-Alder reaction. To predict the relative rates of reaction of dienes, use these rules.
Isolated and cumulated dienes may react as dienophiles, but they cannot react as dienes. Acyclic dienes may rotate around a single bond to become s-cis, but some dienes are locked in the s-trans conformation in Lab 1 melting point structures and cannot react.
|Hemosense Capillary Tubes Microsafe 15ul 50/bg - Model 200235 - Quantity 1||Recrystallization and Melting Point Determinations. Melting Point of 4-Chloroaniline.|
|Melting point determination video||To identify the unknown and the purity of the organic compounds.|
|This is the full lab report for the course CHEM 223 at Hunter College.||Links Determination of Melting Point Determining the melting point of a compound is one way to test if the substance is pure. A pure substance generally has a melting range the difference between the temperature where the sample starts to melt and the temperature where melting is complete of one or two degrees.|
|CHE L - home page||Melting Point Range Temperature at which the first solid starts to melt to a temperature when the last solid dissolves to a liquid.|
The opposite combination also gives relatively fast reactions, but the starting materials are unusual. In absence of solvent and catalytic effect, regioselectivity depends on presence of partial positive or negative character on the terminal carbon centers of dienes or dienophile.
In this case para will be major product. Convince yourself of this before you continue 2. Addition of two molecules is syn on both components bonds form from same species at the same time. This is shown by the examples below: If both substituents on the diene are Z, then both end up on the same face of the product.
A study of the HOMO and LUMO orbitals for the reactions would probably prove very useful in determining a The preference for the endo product b Substituent effects on the rate of reaction c Substituent effects on the regiochemistry of the reaction. In this lab we will be studying the reaction of cyclopentadiene with maleic anhydride.
From previous knowledge of Diels Alder reactions you should be able to predict the stereochemistry of the products. Cyclic dienes can give stereoisomeric products depending on whether the dienophile lies under or away from the diene in the transition state.
The endo product is usually the major product due to kinetic control. Usually, you will not be allowed to begin the lab until you have completed this assignment — allowance made for the first week.
The reaction, as you will notice, occurs very rapidly. State two characteristics of the starting materials that make them ideal coupling partners for this reaction i.
Write the major product of the following reactions, if there is no product specify why. Keep safety glasses on all the time. The Effect of Purity on Melting Point In this section you will take two compounds cinnamic acid and urea and create mixtures of them to determine what effect this will produce, as well as the extent of this effect depending on the composition of the sample.
Prepare a capillary tube containing urea as well as one containing cinnamic acid. Take the melting point of each and compare it to the "Houston" values which your TA will have.
Repeat if the values are not correct. Once the two pure melting points have been determined find a partner and together prepare 3 samples: Take the melting point of each of these mixtures.
Plot the graph of melting point vs. You can prepare a large batch of sample and share the materials among yourselves Take 10mg urea and 90 mg cinnamic acid for 1st sample and mix it together, ratio should be same.
Determination of an Unknown Substance In this portion of the lab you cannot determine the identity of an unknown by comparing its melting point with the melting point of the three possible compounds. Mixing characteristics will be used instead to determine the identity.
Prepare three capillary tubes in the following manner. Take a piece of weighing paper and mix a small amount of the unknown with a small amount of the sample of diphenylacetic acid 1: Place this in a capillary tube.
Then on a new piece of weighing paper, weigh a small amount of the unknown and mix it with a small amount of adipic acid. Place these three capillary tubes in the melting point apparatus and record in detail what occurs to each tube and at what temperature.
Using this knowledge determine the identity of the unknown. Experimental Procedure for Diels-Alder Cyclopentadiene dimerizes at ambient conditions.1) Determining the melting point of trans-Cinnamic acid, Urea and a mixture of both and observing the changes in each due to and ³impurities´ present 2) Identifying and unknown by comparing the melting point ranges of pure substances with that of their mixtures 3) Determining the melting range of an unknown compound given by your instructor.
Melting point of mixture of unknown compound and known compound If the melting point is the same/similar to the melting point of the unknown compound or the known compound alone, then they are identical. 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.
2. once the two pure melting points have been determined find a partner and together prepare 3 samples: one of urea: cinnamic acid, one of urea: cinnamic acid, and one of urea: cinnamic acid.
take the melting point of each of these mixtures.
plot the graph of melting point vs. the composition of the sample. note: you can prepare. 1 Experiment 2: Melting Points and the Identification of an Unknown and Cholesterol from Human Gallstones Part 1.
Melting Points and the Identification of an Unknown Read pp , Chapter 14, (especially page , ) in LTOC and view a video about this technique at. Melting point is the range of temperatures in which a sample is converted from a solid to a liquid.
In Lab 1, how did we analyze melting points? We used a melt-temp device with a capillary tube (sample holder), and mercury thermometer.