Discussion: E-stilbene is a molecule molecule consisting of carbon-carbon double bond with a phenyl functional group attached to each carbon on opposite sides of the double bond. Thus, since this molecule is an alkene, the electrophilic addition of bromine causes the bromine to break and add to the carbon carbon double bond. This mechanism essentially can be considered to have two routes, but three different products. One route will use from a three membered ring (cyclic) with a bromine cation, which will in turn from a meso product (Meso-stilbene dibromide) due to the Sn2 (2nd order bimolecular) addition of bromine, as bromine can only attack the carbon from the opposite side. The meso product has a 1R 2S configuration at its stereoisomers. A meso product is one that contains multiple stereocenters, however, can not rotate plane polarized light because it is superimposable on its …show more content…
The second (SN1, unimolecular) mechanistic route using a carbon cation instead of a bromine cation (acyclic). Therefore, in this case the bromine anion is able to add to the carbocation from either above or below, thus leading to a syn addition or anti addition. If the bromine attacks from below, this causes a racemic mixture to form as the product, that is a mixture of equal arts of the RR (D isomer) form and SS (L isomer) form of the product, which are enantiomers of one another. The RR and SS isomers differ in that the bromine molecules are oriented in the same direction in each individual molecule and opposite directions in relation to one another, therefore, the chical centers rotate plane polarized opposite directions with equal magnitude .If the bromine attacks from above, the meso product will be formed.The meso isomer is a diastereomer of both the D and L isomers. Whether the bromine molecule attacks from above or below simply depends on the random chance of the orientation of the bromine when it comes into contact with the
The competing enantioselective conversion method uses each enantiomer of a kinetic resolution reagent, in this case R-HBTM and S-HBTM, in separate and parallel reactions, where the stereochemistry of the secondary alcohol is determined by the rate of the reactions. When using the CEC method, the enantiomer of the secondary alcohol will react with one enantiomer of the HBTM acyl-transfer catalyst faster than with the other HBTM enantiomer. The mnemonic that identifies the absolute configuration of the secondary alcohol is as follows: if the reaction is faster with the S-HBTM, then the secondary alcohol has the R-configuration. In contrast, if the reaction is faster with the R-HBTM, then the secondary alcohol has the S-configuration. Thin layer chromatography will be used to discover which enantiomer of HBTM reacts faster with the unknown secondary alcohol. The fast reaction corresponds to a higher Rf spot (the ester) with a greater density and a slower reaction corresponds to a lower Rf spot with high de...
Reacting 1-butanol produced 2-trans-butene as the major product. 1-butanol produces three different products instead of the predicted one because of carbocation rearrangement. Because of the presence of a strong acid this reaction will undergo E1 Saytzeff, which produces the more substituted
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.
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
activation energy than what is required to turn camphor into borneol. Though borneol is the more stable product, the energy requirements to form isoborneol are lower because the borohydride is adding to the less sterically hindered point on the carbonyl carbon. The product made is then mostly (85%) isoborneol. More borneol would be expected if more energy was available during the reaction.
In this lab 4-tert-butylcyclohexanone is reduced by sodium borohydride (NaBH4) to produce the cis and trans isomers of 4-tert-butylcyclohexanol. Since the starting material is a ketone, NaBH4 is strong enough to perform a reduction and lithium aluminum hydride is not needed. NaBH4 can attack the carbonyl group at an equatorial (cis) or axial (trans) position, making this reaction stereoselective. After the ketone is reduced by the metal-hydride, hydrochloric acid adds a proton to the negatively charged oxygen to make a hydroxyl group. The trans isomer is more abundant than the cis based on the results found in the experiment and the fact that the trans isomer is more stable; due to having the largest functional groups in equatorial positions.
In order to separate the mixture of fluorene, o-toluic acid, and 1, 4-dibromobenzene, the previously learned techniques of extraction and crystallization are needed to perform the experiment. First, 10.0 mL of diethyl ether would be added to the mixture in a centrifuge tube (1) and shaken until the mixture completely dissolved (2). Diethyl ether is the best solvent for dissolving the mixture, because though it is a polar molecule, its ethyl groups make it a nonpolar solvent. The compounds, fluorene and 1, 4-dibromobenzene, are also nonpolar; therefore, it would be easier for it to be dissolved in this organic solvent.
The most classic and standard procedure for producing esters is the Fisher-esterification reaction. Discovered in 1895 by German chemists Emil Fischer and Arthur Speier 4, this reaction involves refluxing a carboxylic acid and an alcohol in the presence of an acid catalyst. In order to drive the equilibrium towards the products, the water from the dehydration process must be removed and there must be an excess amount of alcohol. A vast range of carboxylic acids may be used for this reaction however the type of alcohols are limited. Primary and secondary alcohols are most frequently used in esterification reactions, tertiary alcohols are steric ally hindered usually resulting in poor yields5 and tend to undergo elimination reactions instead. In this rea...
The 1-methylcyclohexene product is the major product because of its increased stability due to hyperconjugation along the pi bond. The alkene of this product is trisubstituted on the pi bond which is more stable than the bisubstitution on the pi bond of 1-methylcyclohexene which is the minor product.
The solution is then stirred with a glass rod and put to cool in an ice-water bath before the slow addition of 1.0 mL of concentrated sulfuric acid (H2SO4) into the cold mixture in order to prevent the transpiration of undesired side reactions. In a separate test tube, 1-2 mL of 3 M aqueous sodium hydroxide solution can also be placed in the ice bath for extraction later on. After the mixture of NaBr, H2SO4 and 2-phenylethanol has been cooled and mixed, a solid will form. At this point, the application of the method of reflux can commence in order to both increase the reaction rate and to prevent any liquids from being evaporated, due to constant application of heat. With the apparatus set up (in addition to making sure all joints are well sealed, excluding the condenser top), the vial can then be put out of the ice bath, and put to warm. With stirring, all of the solid will eventually dissolve, and with constant heating, the mixture will gently reflux at around 160 ºC (using thermometer in the metal block to confirm), where the biphasic reaction mixture can then vigorously be stirred (with certain
Although some of the results obtained were not totally satisfactory, the general trend expected was persistent. Fluorenone as the limiting reagent was rapidly consumed by the Sodium Borohydride (NaHB4), this is confirmed by noticing the rapidly diminishing activity of Fluorenone, to the point that on the 3rd TLC plate Fluorenone is already absent (consumed by the reaction). One rationale Fluorenone was so rapidly consumed during the reaction, it is because, a hydrogen from the borohydride first attacks the carbonyl group on the Fluorenone molecule, leaving the oxygen with a nucleophilic site. Such a nucleophilic site can then speed up the reaction to the point that after 90 seconds all Fluorenone was consumed; methanol (CH3OH) is attracted
In this experiment, an acid (Benzoic acid), a base (Ethyl 4- Aminobenzoate) and a neutral compound (9-Fluorenone) were extracted from a mixture. HCl was the acid used to separate the base from the mixture, by forming an organic layer, which contained the acid, the neutral compound, and an aqueous layer that contained the base. NaOH was the base that was used to separate the acid from the neutral compound, which resulted in an organic layer containing the neutral compound and an aqueous layer containing the acid. After this a base was then added to the first aqueous layer containing the base, and an acid added to the second aqueous layer containing the acid. The percent recovery of each compound was then evaluated. The basic component, Ethyl
When reacting with different solvents, the relative ratio of β-bromostyrene isomers can give a hint about the mechanisms the reaction underwent. By an atom attaching to either a cis or trans side of a molecule, the production of different isomers occurs. Using stereochemistry, there are clues that can be gathered about the mechanism used. In order for the elimination reaction to occur there are two options, either E2 or E1 pathway. Both of these pathways have characteristics that must be present for the reaction to occur. The E2 reaction need the molecule to have anti-coplanar stereochemistry, while the E1 reaction needs a strong leaving group, which will create a tertiary or secondary carbocation. The E2 reaction also needs a strong base in
Introduction Organometallic compounds are substances that contain carbon-metal bonds. Metals found in these compounds are typically lithium (Li), magnesium (Mg), copper (Cu), mercury (Hg), or other transition metals. Organometallic compounds are also known as Grignard reagents (1).
This is used in removing substituents after they have served their purpose. e.g. are the retro - Bingel reaction and retro - prato reaction *8. Carbene Additions:* A Carbene is a molecule containing a neutral carbon atom with a valance of two and two unshared valence electrons. Methylene (H2C:) is the simplest form.