Wittig reactions allow the generation of an alkene from the reaction between an aldehyde/ketone and a ylide (derived from phosphonium salt).The mechanism for the synthesis of trans-9-(2-phenylethenyl) anthracene first requires the formation of the phosphonium salt by the addition of triphenylphosphine and alkyl halide. The phosphonium halide is produced through the nucleophilic substitution of 1° and 2° alkyl halides and triphenylphosphine (the nucleophile and weak base) 4 An example is benzyltriphenylphosphonium chloride which was used in this experiment. The second step in the formation of the of the Wittig reagent which is primarily called a ylide and derived from a phosphonium halide. In the formation of the ylide, the phosphonium ion in benzyltriphenylphosphonium chloride is deprotonated by the base, sodium hydroxide to produce the ylide as shown in equation 1. The positive charge on the phosphorus atom is a strong EWG (electron-withdrawing group), which will trigger the adjacent carbon as a weak acid 5 Very strong bases are required for deprotonation such as an alkyl lithium however in this experiment 50% sodium hydroxide was used as reiterated. Lastly, the reaction between ylide and aldehyde/ketone produces an alkene.3 (Eq. 1) As shown in equation 2, the reaction between the phosphonium salt and the sodium hydroxide produces the ylide/carbanion that is stabilized due to the positive charge on phosphorus and the conjugation that occurs in the benzene ring as shown by the structure B in equation 2. The ylide produced also has a resonance form (B’). The resonance form is advantageous because it contains no formal charge and the double bond it contains results in the same position of the double bond in the final a... ... middle of paper ... ...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 percent yield of products that was calculated for this reaction was about 81.2%, fairly less pure than the previous product but still decently pure. A carbon NMR and H NMR were produced and used to identify the inequivalent carbons and hydrogens of the product. There were 9 constitutionally inequivalent carbons and potentially 4,5, or 6 constitutionally inequivalent hydrogens. On the H NMR there are 5 peaks, but at a closer inspection of the product, it seems there is only 4 constitutionally inequivalent hydrogens because of the symmetry held by the product and of this H’s. However, expansion of the peaks around the aromatic region on the NMR show 3 peaks, which was suppose to be only 2 peaks. In between the peaks is a peak from the solvent, xylene, that was used, which may account to for this discrepancy in the NMR. Furthermore, the product may have not been fully dissolved or was contaminated, leading to distortion (a splitting) of the peaks. The 2 peaks further down the spectrum were distinguished from two H’s, HF and HE, based off of shielding affects. The HF was closer to the O, so it experienced more of an up field shift than HE. On the C NMR, there are 9 constitutionally inequivalent carbons. A CNMR Peak Position for Typical Functional Group table was consulted to assign the carbons to their corresponding peaks. The carbonyl carbon, C1, is the farthest up field, while the carbons on the benzene ring are in the 120-140 ppm region. The sp3 hybridized carbon, C2 and C3, are the lowest on the spectrum. This reaction verifies the statement, ”Measurements have shown that while naphthalene and benzene both are considered especially stable due to their aromaticity, benzene is significantly more stable than naphthalene.” As seen in the reaction, the benzene ring is left untouched and only the naphthalene is involved in the reaction with maleic
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
However, it provided insight in the context of Diels-Alder reaction at that time[8] and confirmed the morphine structure proposed by organic chemist Robert Robinson[9]. As a result, many chemists eventually discovered an efficient way to produce morphine. The most prominent of which was developed by Kenner C. Rice which proceeded to make 30% of the product with 14 steps[10]. His method is based on the biomimetric route that follows the Grewe cyclization which corresponds to the morphine biosynthesis[10], as illustrated in Figure
The dehydration of 2-butanol, a secondary alcohol, progresses readily in the presence of a strong acid like concentrated sulfuric acid (H2SO4). The reaction is completed via the E1 mechanism. Initially, the hydroxyl group is a poor leaving group, but that is remedied by its protonation by the acid catalyst (H2SO4) converting it to a better leaving group, H2O. The loss of this water molecule results in a secondary carbocation intermediate that continues to form an alkene in an E1 elimination. If the elimination happens with either protons on the terminal methyl group, the resultant product is 1-butene, a Hoffman product (monosubstituted alkene). In contrast, elimination of either β-hydrogens by the conjugate base of sulfuric acid (HSO4---) on the methylene group leads to an alkene that is disubstituted. Either the cis- or trans-2-butene can form depending which hydrogen is deprotonated. These are the Saytzeff products since they are the most substituted ones. In this case, the trans-alke...
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)
...lpentane. 1H NMR (CDCl3, 200 MHz) δ 2.1-1.8 (nonet, 1H), 1.7 (d, 6H), 1.6 (s, 6H), 0.95-0.90 (d, 2H). 3-chloro-2,4-dimethylpentane. 1H NMR (CDCl3, 200 MHz) δ 3.6-3.5 (t, 1H), 2.6-2.4(octet, 2H) 1.1-1.0 (d, 12H). IR (cm-1) 2962.42, 743.14, 708.01. GC (TCD) 4.2 m (100%).
During this week’s lab, both the cis and trans enantiomers of 2-methylcyclohexanol will be produced through the reduction of 2-methyclcyclohexanone with sodium borohydride. Once the product is formed, NMR signals are used to examine the product of this reduction by observing the cis and trans location of the CH2OH group. The integration of the signal will then be examined and to show the ratio of cis and trans product that is formed through this reaction.
The objective of this report is to calculate the activation energy for the molecule of HALS reaction using GAUSSIAN 09 via the WebMO interface. There have been assumed that the transition state can be obtained through the reaction as in (Scheme3). By using the program and format (opt=(TS,calcfc,noeigen) freq=noraman) , the structure was optimized and formed as a ring shape in order to be able to transfer Hydrogen from Carbon to nitrogen in the molecule. It also was attempted re-drawing some of the N-O and O-C bond lengths/angles to try and get that final H down closer to the N. Consequently, the result of transferring hydrogen directly to nitrogen was slightly very weak resulting from the frequency output (the first one is negative) given a quite low number by -252 (cm-1). Beside that, it was animated the molecule from the program and did not look like a H- transfer is going to N (Figure 3 (A)). That is because the strongly effect of methyl group located surrounding into two sides of nitrogen led not to...
3,7-dimethylpurine-2,6-dione, more commonly known as theobromine is an alkaloid. Theobromine gets its name from Theobroma which is comprised of two Greek words, theo (god) and broma (food). It is composed of carbon, oxygen, nitrogen and hydrogen atoms, the molecular formula being C7H8N4O2. All these atoms together produce a molecular weight of 180.167g/mol. Theobromine has a hexagonal part and a pentagonal part connected by two carbons with a double bond between them. The interior angles for the hexagonal portion are all 120. There are two ketones on the second and sixth atom’s, both are carbons because they are carbonyl groups. They both form 120 angles with their respective carbons. Also on the hexagonal part is a hydrogen attached to a nitrogen bonded at an angle of 107 up (not on the same plane) because of the lone pair of electrons. Both the hexagonal and pentagonal part have a methylpurine group on atoms 3 and 7 which are both nitrogen causing them to have a bond angle of 107 up (not on the same plane) because of the lone pair of electrons. These two groups have a tetrahedral shape making all the angle around the carbon to be
The 1H NMR spectrum shows that there are 18 protons in 11 different proton environments. This fits with the Diels-Alder reaction taking place a...
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.
The spots moved 3.8cm, 2.3cm, 2.1cm, 1.8cm, and 2.5 cm, for the methyl benzoate, crude product, mother liquor, recrystallized product, and isomeric mixture, respectively. The Rf values were determined to be.475,.2875,.2625,.225, and.3125, for the methyl benzoate, crude product, mother liquor, recrystallized product, and isomeric mixture, respectively. Electron releasing groups (ERG) activate electrophilic substitution, and make the ortho and para positions negative, and are called ortho para directors. In these reactions, the ortho and para products will be created in a much greater abundance. Electron Withdrawing groups (EWG) make the ortho and para positions positive.
...icted α-methyl-2-naphthalenemethanol. Probably the most obvious clue that corresponded to this secondary alcohol was the seven integrated hydrogens within the aromatic region of 7.5-7.9 ppm. This compound was the only one that had seven hydrogens belonging to naphthalene. The other two secondary alcohols 3-methoxy-α-methylbenzyl alcohol and 4-bromo-α-methylbenzyl alcohol have only four aromatic hydrogens.
Enantiomers, a type of isomer, are non-superimposable, mirror images of each other. Diasteriomers, another type of isomer, are non-superimposable, non-mirror images of each other. Dimethyl maleate and dimethyl fumarate are diasteriomers, as they are not mirror images but instead vary in the orientation of the carbomethoxy groups around the double bond. Dimethyl maleate is the cis-isomer because both groups are on the same side and dimethyl fumarate is the trans-isomer because the two groups are on opposite sides. A bromine free radical mechanism was required for this conversion. First, energy from light is required to create two bromine free radicals from Br2. Then one of the free radicals attacks the double bond in dimethyl maleate, breaking it and creating a carbon radical on the other carbon. The bond then rotates and reforms, freeing the bromine radical and creating the trans-isomer, dimethyl fumarate. Bromine in this reaction is acting as a catalyst in this reaction and then cyclohexane is added at the end to neutralize the bromine free radicals. The activation reaction of the radical reaction is lower than the activation energy of the addition reaction, which is why it occurred more quickly. This reaction was successful because the percent yield was 67.1%, which is greater that 65%. It also demonstrated the expected principles, as the reaction did not occur without the presence of both light and bromine. The dimethyl fumarate had a measured boiling point of 100C to 103C, which is extremely close to the expected boiling point of 102C to
Falak Mdahi Chem 203.2 The Synthesis of Acetanilide from Acetic Anhydride and Aniline Introduction Recrystallization is a technique used to purify solids that contain small amounts of impurities. It is used to isolate pure solids from a supersaturated solution, leaving the impurities in the solvent (1). The solid containing the impurities is placed in a hot solvent and upon cooling the compound precipitates to its purified form while the impurities are left behind in the solvent (1). There are six steps when it comes to undergoing a recrystallization of a solid.