The goal of this lab is to exemplify a standard method for making alkyne groups in two main steps: adding bromine to alkene groups, and followed by heating the product with a strong base to eliminate H and Br from C. Then, in order to purify the product obtained, recrystallization method is used with ethanol and water. Lastly, the melting point and IR spectrum are used to determine the purity of diphenylacetylene. This experiment was divided into two main steps. The first step was the addition of bromine to trans-stilbene. Trans-stilbene was weighted out 2.00g, 0.0111mol and mixed with 40ml of glacial acetic acid in 100ml Erlenmeyer flask on a hot bath. Pyridinium hydrobromide perbromide of 4.00g, 0.0125mol was added carefully into the flask. …show more content…
The mixture was mixed and heated for another two to three minutes and the precipitates formed. The flask was cooled in running water. The precipitates was collected through suction filtration and washed with 30ml of methanol to remove the yellow color. The product was allowed to dry, and the reflux apparatus was set up. The filtrate was disposed down the drain after adding sodium bisulfate and water to remove orange color. Second part of the experiment was the elimination of HBr from Stilbene dibromide. Potassium hydroxide of 1.51g that was weight out and 20ml of ethylene glycol were put in the 100ml round bottom flask, swirled, and warmed until KOH dissolved. The product from the first part along with 2 boiling chips was added into the flask, and the gentle reflux process began and maintained for 20mn. Then, the hot solution was decanted into 250ml Erlenmeyer flask and allowed to cool down to room temperature. Water in the volume of 120ml was slowly added into the flask, and the product separated as a yellow semi-crystallized mass. The mixture was allowed to stand for 15mn in an ice bath. Suction filtration was performed on the mixture to obtain the crystalline. Lastly, in order to purify the product, the recrystallization method was used. The product was dissolved using approximately 8ml of warm ethanol. Few drops of water were added in the mixture on the hot plate until the mixture became cloudy. The mixture was allowed to cool down to room temperature, and then the crystals of 0.93g, 0.00522mol, 47.0% yield were collected by suction filtration, allowed to dry, and weight. The melting point determination and IR spectrum were performed. From table 1, Diphenylacetelene (0.93g, 0.00522mol, 47.0% yield) was obtained as a result of synthesis between trans-stilbene and bromine and later with potassium hydroxide and ethylene glycol. The calculated theoretical mass was 1.98g; however, the mass obtained is less than half of the expected mass. Most of the product was lost in filtrate during the recrystallization process with the potential of human error into consideration. The literature melting point of pure diphenylacetelene was 62C; however, the melting point of the experimental diphenylacetelene was from 62.5 to 64.5 C. Even though the experimental was close to the acceptable range of purity, the product obtained still contained some impurities in there. The impurities might be the ethanol that was used in recrystallization process for cleaning. Another assumptions were that during the recrystallization process, the impurities might be trapped in the crystal since the solution was not able to stay in room temperature long enough for fully recrystallizing the product before putting in ice bath. The IR spectrum of pure diphenylacetelene resulted in the presence of 2 peaks C-H (sp3), which were at position between 2850-2880 and 2900-2960 cm-1 and had medium and strong intensity, respectively.
A weak peak was at a position between 1600-1620 cm-1 can also be seem in the IR, which was likely to be aromatic C=C functional group that was from two benzene rings attached to alkynes. On the other hand, the IR spectrum of the experimental diphenylacetylene resulted in 4 peaks. The first peak was strong and broad at the position of 3359.26 cm-1, which was most likely to be OH bond. The OH bond appeared in the spectrum because of the residue left from ethanol that was used to clean the product at the end of recrystallization process. It might also be from the water that was trapped in the crystal since the solution was put in ice bath during the recrystallization process. The second peak was weak, but sharp. It was at the position of 3062.93 cm-1, which indicated that C-H (sp2) was presence in the compound. The group was likely from the C-H bonds in the benzene ring attached to the alkyne. The remaining peaks were weak and at positions of 1637.48 and 1599.15 cm-1, respectively. This showed that the compound had aromatic C=C function groups, which was from the benzene rings. Overall, by looking at the functional groups presented in the compound, one can assume that the compound consisted of diphenylacetelene and ethanol or
water. The exemplification of a standard method for making alkyne groups in two main steps consisted of the addition of bromine into trans-stilbene and the elimination of Hbr from stilbene dibromide was performed. The diphenylacetylene (0.93g, 0.00522mol, 47.0%yield) was obtained. The percentage yield was really low due to the loss of product in filtrate during suction filtration process in recrystallization step. The products still contained some impurities, which were either water, ethanol, or both since O-H bond was presented in IR spectrum; however, the impurities was very little because the melting point of the experimental product only deviated approximately 3C from the literature melting point. Overall, the objective of this lab was successfully obtained.
The goal of this experiment is to determine which products are formed from elimination reactions that occur in the dehydration of an alcohol under acidic and basic conditions. The process utilized is the acid-catalyzed dehydration of a secondary and primary alcohol, 1-butanol and 2-butanol, and the base-induced dehydrobromination of a secondary and primary bromide, 1-bromobutane and 2-bromobutane. The different products formed form each of these reactions will be analyzed using gas chromatography, which helps understand stereochemistry and regioselectivity of each product formed.
In a small reaction tube, the tetraphenylcyclopentadienone (0.110 g, 0.28 mmol) was added into the dimethyl acetylene dicarboxylate (0.1 mL) and nitrobenzene (1 mL) along with a boiling stick. The color of the mixed solution was purple. The solution was then heated to reflux until it turned into a tan color. After the color change has occurred, ethanol (3 mL) was stirred into the small reaction tube. After that, the small reaction tube was placed in an ice bath until the solid was formed at the bottom of the tube. Then, the solution with the precipitate was filtered through vacuum filtration and washed with ethanol. The precipitate then was dried and weighed. The final product was dimethyl tertraphenylpthalate (0.086 g, 0.172mmol, 61.42%).
...e 3. Both letters A and B within the structure of trans-9-(2-phenylethenyl) anthracene, that make up the alkene, have a chemical shift between 5-6 ppm and both produce doublets because it has 1 adjacent hydrogen and according to the N + 1 rule that states the number of hydrogens in the adjacent carbon plus 1 provides the splitting pattern and the number of peaks in the split signal, which in this case is a doublet.1 Letters C and D that consist of the aromatic rings, both are multiplets, and have a chemical shift between 7-8 ppm. 1H NMR could be used to differentiate between cis and trans isomers of the product due to J-coupling. When this occurs, trans coupling will be between 11 and 19 Hz and cis coupling will be between 5 and 14 Hz, showing that cis has a slightly lowered coupling constant than trans, and therefore have their respective positions in a product. 2
The camphor then went through reduction with sodium borohydride to make isoborneol. This reaction was able to be stereochemically controlled by limiting the amount of heat we provided. The conversion of camphor to isoborneol has a lower
The IR spectrum that was obtained of the white crystals showed several functional groups present in the molecule. The spectrum shows weak sharp peak at 2865 to 2964 cm-1, which is often associated with C-H, sp3 hybridised, stretching in the molecule, peaks in this region often represent a methyl group or CH2 groups. There are also peaks at 1369 cm-1, which is associated with CH3 stretching. There is also C=O stretching at 1767 cm-1, which is a strong peak due to the large dipole created via the large difference in electronegativity of the carbon and the oxygen atom. An anhydride C-O resonates between 1000 and 1300 cm-1 it is a at least two bands. The peak is present in the 13C NMR at 1269 and 1299 cm-1 it is of medium intensity.
In this experiment, four elimination reactions were compared and contrasted under acidic (H2SO4) and basic (KOC(CO3)3) conditions. The acid-catalyzed dehydration was done on 2-butanol and 1-butanol; a 2ᵒ and 1ᵒ alcohol, respectively. The base-induced dehydrobromination was performed on 2-bromobutane and 1-bromobutane; isomeric halides. The stereochemistry and regiochemistry of the four reactions were analyzed by gas chromatography (GC) to determine product distribution (assuming that the amount of each product in the gas mixture is proportional to the area under its complementary GC peak. The three butene products have been verified that they elute in the following order: 1-butene, trans-2-butene, and cis-2-butene.
After performing the second TLC analysis (Figure 4), it was apparent that the product had purified because of the separation from the starting spot, unlike Figure 3. In addition, there was only spot that could be seen on the final TLC, indicating that only one isomer formed. Since (E,E) is the more stable isomer due to a less steric hindrance relative to the (E,Z) isomer, it can be inferred that (E,E) 1,4-Diphenyl-1,3-butadiene was the sole product. The proton NMR also confirmed that only (E,E) 1,4-Diphenyl-1,3-butadiene formed; based on literature values, the (E,E) isomer has peaks between 6.6-7.0 ppm for vinyl protons and 7.2-7.5 ppm for the phenyl protons. Likewise, the (E,Z) isomer has vinyl proton peaks at 6.2-6.5 ppm and 6.7-6.9 ppm in addition to the phenyl protons. The H NMR in Figure 5 shows multiplets only after 6.5 ppm, again confirming that only (E,E) 1,4-Diphenyl-1,3-butadiene formed. In addition, the coupling constant J of the (E,E) isomer is around 14-15 Hz, while for the (E,Z) isomer it is 11-12 Hz. Based on the NMR in Figure 5, the coupling constant is 15.15 Hz, complementing the production of (E,E)
A mixture of 2 mL aniline, 15 mL deionized water and 3 mL acetic anhydride were stirred. After thirty minutes the reaction was complete and the product was completely precipitated out of the solution. Vacuum filtration was used to isolate the crude acetanilide using a 125 mL filter flask and porcelain Büchner funnel. The product was then washed with 2 mL of ice water and left to dry for about twenty minutes. The observed melting point for the crude acetanilide was 114.3 °C - 115.7 °C. The second procedure dealt with finding a suitable solvent to recrystallize the crude acetanilide. A sand bath was set up and 0.5 mL of each solvent was added to 50 mg of acetanilide in four different test tubes. The four solvents used to test the solubility of the acetanilide were water, ethanol, dichloromethane and hexanes. If the solid dissolved in the solvent at room temperature then it was too soluble and that solvent could be eliminated. The acetanilide completely dissolved in ethanol and dichloromethane, therefore eliminating them from being the suitable solvent. If the solid did not dissolve in room temperature then it was placed in the sand bath and left to boil. If the solid dissolved, it was placed in the ice bath and if crystals were observed coming out of the solution then the suitable solvent was found. The suitable solvent was water as the crystals came out once placed in the ice bath. The
In experiment 2, we carried out experiment to observe the reaction of halogenoalkanes with aqueous alkali and water which contains dissolved silver nitrate. Halogenoalkanes are alkanes which have one or more hydrogen atoms replaced by halogen atoms such as fluorine(F), chlorine(Cl), bromine(Br) and iodine(I) which are the elements in group VII in periodic table. Halogenoalkanes have the general formula, RX, whereby R is an alkyl or substituted alkyl group and X is any of the halogen atom. Besides, halogenoalkanes can also be classified into three categories according to what is attached to the functional group such as primary, secondary and tertiary halogenoalkane.
Thickett, Geoffrey. Chemistry 2: HSC course. N/A ed. Vol. 1. Milton: John Wiley & Sons Australia, 2006. 94-108. 1 vols. Print.
When a hydrogen atom in an aliphatic or aromatic hydrocarbon is replaced by halogen atoms then the compounds are termed as haloalkanes and haloarenes. Halogens are the less reactive functional group in comparison to carboxyl or aldehyde group. Therefore, halogen group when attached as a functional group do not bring a drastic difference in the overall physical properties of a compound. However, some differences can be seen as we move down the group in the homologous series of haloalkanes and haloarenes due to the difference in the atomic masses.
14.6 and 34.52 tR and peak number 14 and 162, respectively and 38 other compounds identified in
The frequency is expressed in wavenumbers (cm-1). There are peaks that point downward. A peak corresponds to the frequency of vibration of one particular functional group present in the molecule. Thus, a peak in the spectrum implies a functional group and the number of peaks can imply how many functional groups are there (except for aromatics that produces a series of peaks called overtones). Since one particular functional group has a unique frequency of vibration, infrared spectroscopy is used in identifying the different functional groups present in the molecule. Thus, information about the molecular structure of the compound is revealed.
Heterocyclic chemistry is the branch of chemistry dealing with the synthesis, properties and applications of heterocycles. The name comes from the greek word “heteros” which means “different”. Any of a class of organic compounds whose molecules contain one or more rings of atoms with at least one atom (the heteroatom) being an element other than carbon, most frequently oxygen, nitrogen, or sulfur [1].
Chlorine 1s2 2s2 2p6 3s2 3p5 or [Ne] 3s2 3p5 . Bromine 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5 [Ar] 4s2 3d10 4p5 & Iodine 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p5 or [Kr] 5s2 4d10 5p5