The Wittig reaction, also known as the Wittig olefination, is an organic chemical reaction that allows for the synthesis of an alkene from an aldehyde or a ketone and a phosphonium ylide. This reaction is named after Georg Wittig, who received the Nobel Prize in Chemistry in 1979 for his contributions to the field of chemistry, including the development of the Wittig reaction.
In the Wittig reaction, the phosphonium ylide acts as a nucleophile, reacting with the electrophilic carbon atom of the aldehyde or ketone. The resulting intermediate, known as a Wittig intermediate, undergoes an elimination reaction to form an alkene, as well as a triphenylphosphine oxide byproduct.
One of the key benefits of the Wittig reaction is its high regioselectivity, meaning that it can selectively produce a particular isomer of the alkene. This is due to the stereochemistry of the phosphonium ylide, which can be controlled through the synthesis of the ylide.
The Wittig reaction can be carried out in the presence of a variety of solvents, such as ethers, tetrahydrofuran, and chloroform. The choice of solvent can affect the yield and stereoselectivity of the reaction.
In a laboratory setting, the Wittig reaction can be performed by mixing the aldehyde or ketone, phosphonium ylide, and solvent in a round-bottomed flask. The mixture is then heated to the desired temperature, typically between 50 and 100 degrees Celsius, and allowed to react for a specified amount of time. The progress of the reaction can be monitored through the use of thin-layer chromatography or nuclear magnetic resonance spectroscopy.
After the reaction is complete, the mixture is cooled and the product is isolated through the use of standard purification techniques, such as crystallization or distillation. The purity of the product can be confirmed through the use of analytical techniques, such as infrared spectroscopy or mass spectrometry.
Overall, the Wittig reaction is a useful synthetic tool for the production of alkenes, and has found wide applications in the fields of organic chemistry and drug discovery. It is an important reaction to understand and be able to carry out in the laboratory, and a successful Wittig reaction lab report should detail all of the necessary information, including the materials and methods used, the results obtained, and a discussion of the implications of the findings.
Wittig Reaction Lab links.lfg.com
A small amount of the solid was collected and dissolved in CH2Cl2 for TLC analysis. Our TLC spots, though they show a slight but noticeable trend in the retention factors of our unknowns across multiple fractions, reveal the presence of multiple contaminants, including triphenylphos- phine oxide spots Rf 0 in each of our fractions when in theory the product should elute before triphenylphosphine oxide. The stereoselectivity of the reaction is predicated on the stability of triphenylphosphonium ylide, which determines which of two ring intermediates form: the sterically-unfavoredcisintermediate that forms via a fast yet reversible process, or the slow, irreversibletransintermediate. Between our three separate analysis techniques, we can conclude that the most likely source of the significant error in this experiment was a poor choice of eluted fractions for purification from the column chromatograph; though we should expect our product to elute before triphenylphosphine oxide due to decreased interaction with the polar silica gel stationary phase. As a result, the greatest concentration of our products could most likely be found among the earlier fractions collected, whereas our choice to purify the later fractions, ironically, produced mostly impurities and side products — the exact opposite of the point of the column chromatography. The purity of E-Stilbene could have been increased by allowing the reaction to perform longer and to use a faster reactant such as Bromine.
post lab 8 wittig
The experiment was performed and allowed for the demonstration of the Wittig reaction using 9-Anthraldehyde and. There is a strong indication of E, E -1,4-diphenyl-1,3-butadiene, but weaker peaks can be attributed to the E, Z isomer. The Wittig reaction uses a phosphorous ylide as its reagent and the vital step is its formation of the oxaphosphetane cyclic intermediate. Wittig reaction mechanism involving the benzyltriphenylphosphonium derived ylide and cinnamaldehyde. The alkene in the final product contains unsaturation of the olefinic pi bond thus enabling the product to possess the ability to absorb light. This ylide will then be used to react with trans-cinnamaldehyde to generate 1,4-diphenyl-1,3-butadiene Figure 1. Because ylides contain by definition adjacent positive and negative charges a positive on the phosphonium, and a negative on the carbon adjacent to the residue , R groups that can better stabilize the adjacent negative charge produce more stable ylides.
