Wittig Reaction Lab Report

The prior state of charge is restored when the leaving group (LG) departs with an electron pair. The principal product in this case is R-Nuc. In such reactions, the nucleophile is usually electrically neutral or negatively charged, whereas the substrate is typically neutral or positively charged. An example of Nucleophilic substitution is the hydrolysis of an alkyl bromide, R-Br, under basic conditions, where the attacking nucleophile is the base OH− and the leaving group is Br−. R-Br + OH− → R-OH + Br− Nucleophilic substitution reactions are commonplace in organic chemistry, and they can be broadly categorized as taking place at a carbon of a saturated aliphatic compound carbon or (less often) at an aromatic or other

TLC was used to identify the actual unknown product as well as other products/reactants present in the filtered solution. The procedure was conducted by placing a TLC plate in a developing chamber that is filled with a small amount of solvent. The solvent cannot be too polar because it will cause spotted compounds on the TLC plate to rise up too fast, while a very non-polar solvent will not allow the spots to move. The polarity of the spots also determines how far it moves on the plate; non-polar spots are higher than polar ones. After spots on the TLC form, the Rf values are calculated and used to analyze the similarity of the compounds.

One thought was that the discrepancy was due to the magnetic dipole of nucleons, but since the values were of the order of the Bohr magneton which is about 2000 times more than those expected from the nucleus the thought was ruled

It forms a complex with HBr and extracts it from the aqueous phase into the organic phase where the alkene is. This dehydrates the acid, making it more reactive so that the addition reaction is possible. Rapid stirring is required in order to maximize the surface area

The third step is where the oxyanion electrons reform the bond with the aromatic amino acid. Then the bond between the carboxyl-terminus of the amino acid and the n-terminus of the residue is cleaved and its electrons are used to take out the hydrogen of the nitrogen on the Histidine 57. The c-terminal side of the polypeptide is free to dissociate form the active site. Step four is basically just where water can now enter and bind to the active site through hydrogen bonding, which is between the hydrogen atoms of water and the Histidine-57 nitrogen. The fifth step is the step where the water and oxygen make a nucleophilic attack on the carbonyl carbon of the acyl-enzyme intermediate.

The product of the reaction was purified by recrystallization and characterized by both NMR spectra and melting point

This problem could have arisen from an overly dilute extract used when running the TLC. Prior to conducting TLC, the extracts S2 and S3 were used in the UV-vis spectroscopic analysis. Failing to consider the use of the samples for TLC afterwards, huge proportions of both extracts were disposed off after the spectroscopic analysis. Even though the remaining extract volumes were concentrated by evaporating off the solvent, the number of moles of compounds present were still not concentrated enough for clear visible spots to be obtained from the TLC

Tertiary alkyl halides tend to give a mixture with both inverted and retained configurations at reaction centers. This is because this reaction proceeds through a stable carbocation intermediate and the carbon at the reaction center goes to sp2 hybridized state (planar geometry). The incoming nucleophile can attack from both sides of the plane and can give two products with retained and inverted configuration. If there is a partial interaction with the leaving group (nucleofuge) with carbocation there will be more product with inverted configuration and if there is no interaction with leaving group racemic mixture can be obtained. The rate of the reaction depends on the formation of a carbocation (which is the slow step) and there is one molecule

ABSTRACT The Diels-Alder reaction has been an area of great research interest with regards to enhancing enantioselectivity in the reaction by use of various catalysts and reaction conditions. INTRODUCTION In organic chemistry, a Diels-Alder reaction refers to a 4, 2 cycloaddition between a diene consisting of alternating double bonds and a substituted alkene (the dienophile) resulting in a substituted cyclohexene system. The reaction is often used to reliably control regioselective and enantioselective aspects in organic synthesis.

The reaction to synthesize benzocaine was known as a Fisher esterification reaction. The Fisher esterification was reaction between alcohol and carboxylic acid in the presence of acid. The reaction was used to form an ester. In the experiment, sulfuric acid acted as a catalyst and necessary for this reaction to occur. There was a change between the –OH group of carboxylic acid to an –OCH2CH3 group in the reaction.

The objective of the experiment completed was to form the product 9,10-dihydroanthracene-9,10-α,β-succinic anhydride from anthracene and maleic anhydride. The reaction that took place is named a Diels-Alder reaction, defined as an addition reaction in which a diene unites with a double or triple bond of an unsaturated compound to form a 6-membered-ring. The following reactions below depict the ways in which dienes and dienophiles join to form products. Anthracene functioned as a diene and maleic anhydride functioned as the dienophile. Xylene was used as a solvent that provided a quicker way of reaction between the two starting materials.

A decrease in melting point occurs with an impure substance. If she is not convinced by those two melting points, she can create a solid derivative of 2,4-DNP to obtain a third melting point to compare. Furthermore, she could perform the Tollens’ test or the Iodoform test just to be sure she is coming to the correct conclusions. 4- A student finds that the 2,4-DNP derivative of his unknown melts at 155-156°C, and the oxime melts at 68-69°C.

The goal of this experiment was to isolate three different molecules (acidic, basic, and neutral) from a mixture and identify their molecular structure. This was accomplished by using acid/base liquid extraction and H NMR analysis. The neutral component of the unknown mixture #191 was fluorenone. This was evident due to an H NMR spectra that had a high presence of hydrogen signals in the 7.2- 7.7 ppm range. Chemical shift values for fluorenone stated in the lab manual were 7.27, 7.47, 7.48, and 7.6 (CITE), indicating that the corresponding H NMR spectra for the neutral unknown is of this chemical.