Uv Spectrum of SPF

According to absorbance @ 312 nm vs. log₁₀ (SPF), Coppertone SPF 30 represented a greater light absorbance at 1.826 nm when compared to non-brand SPF 30 (0.834 nm). Coppertone SPF 70 also had a greater light absorbance at 0.945 nm when compared to non-brand SPF 70 (0.891). The other compounds couldn’t be compared in this case because one was SPF 15 and the other was SPF 50. When molar extinction coefficients of the compound were compared, the active ingredient appeared to be 2-Ethylhexyl salicylate with a concentration molarity of 4 x 10^-5 mol/L and a molar extinction coefficient of 7.96 x 10⁴. 2-Ethylhexyl-p-cinnamate had a concentration molarity of 3.448 x 10^-5 mol/L and a molar extinction coefficient of 4.17 x 10⁴. When plotted, log₁₀ SPF vs. absorbance @ 312 nm does not have much of a linear relationship; however, Coppertone increases from 15 to 30 SPF and non-brand increases from 30 to 50 SPF. This increase represents somewhat of a linear relationship—as SPF increases, absorbance increases—for the smaller SPF’s of each brand. The relationship between UV and molecular structure is explanatory by the concept of conjugation—alternating double and single bonds resulting in π bonds that are delocalized. Structures that include more conjugation absorb UV radiation of lower energy and longer wavelength. If a compound with a double bond absorbs UV energy, an electron in a Pi bonding orbital is promoted to a higher energy orbital—anti-bonding orbital. The conjugation of one double bond with another double bond increases the number of orbitals in the system and reduces the energy difference between the occupied and unoccupied orbitals. Therefore, upon conjugation, the amount of UV energy needed to move the electron decreases and the wavelength of the UV radiation increases. According to UV data, Coppertone is more effective in SPF 15 and 30. Coppertone SPF 70 is similar to all the non-brand SPFs. Coppertone SPF 15 and 30 absorb the largest amount of light—1.476 and 1.826, respectively.

Conclusion: After UV analysis, Coppertone SPF 15 and 30 absorbed the most light significantly (as represented on attached graph). The 3 non-brand SPFs were oddly similar, and Coppertone 70 had an absorbance similar to the non-brand SPFs. When molar extinction coefficients were compared, 2-ethylhexyl salicylate appeared to have a greater molar extinction coefficient (7.96 x 10⁴) and a greater concentration (4.0 x 10^-5 mol/L) than 2-ethylhexyl-p-cinnamate—molar extinction coefficient: 4.17 x 10⁴, and concentration (3.448 x 10^-5 mol/L).

Trifluoroacetate Esters

In this experiment, the unknown alcohol (5) was reacted with trifluoroacetic anhydride for form a trifluoroacetate ester and trifluoroacetic acid. Alcohol 5 was 2-pentanol, which underwent a nucleophilic substitution reaction of exothermic esterification to form 2-pentyl trifluoroacetate and trifluoroacetic acid, which has a pKa of -0.25. The alcohol was determined to be 2-pentanol because the trifluoroacetate ester product had a boiling point of 112 deg.C and a refractive index value of 1.3453. The literature provided had a boiling point of 120 deg.c and a refractive index value of 1.3456. Because the boiling point can vary more due to ranging and contamination, the determination was based more upon the refractive index value with coordination to the boiling point. The actual product mass was 0.713 g, and the theoretical yield was 1.0075 g (3.88 x 10 -3 mol). This resulted in a percent yield of 70.8%. The deduction of percent yield accumulated through the steps of the reaction. Product could have been lost in the 2 extractions of aqueous layers, the transfer of the organic layer to the test tube for drying, and the transfer of the organic layer to a 3.0 mL vial for weighing.

Conclusion:

In this lab, an esterification reaction of unknown alcohol #5 and trifluoroacetic anhydride was successfully run in order to form 2-pentyl trifluoroacetate and trifluoroacetic acid. The unknown alcohol was determined by the refractive index value of the ester—1.3453—and the boiling point—112 deg.c. The 2-pentyl trifluoroacetate had a percent yield of 70.8% due to multiple extractions and transferring the product.

Synthesis and Stereochemistry of 2,2-dimethyl-1,3-dioxolane

In this experiment, Benzil was reduced with NaBH4, and the diol—Hydrobenzoin—was converted to an acetal of hydrobenzoin—2,2-dimethyl-1,3-dioxolane. The hydryobenzoin product weighed 0.290 g, or 0.00135 mol. The theoretical yield of hydrobenzoin was 0.32139 g, and the percent yield was 90.3%. The melting point was 134.8 degC. According to the melting point, the hydrobenzoin isomer was meso—R,S. because the product was meso, the proton NMR for the acetal revealed 2 methyl peaks. The Jones test for hydrobenzoin was negative, but because the benzyl starting product had such a low mp of ~95 degC, the test was not reliable for the hydrobenzoin product. The basis of alcohol (diol) should focus on mp of hydrobenzoin, which obtained an R,S meso configuration. The weight of the acetal product—dioxolane—was 0.222g, or 8.73 x 10-4 mol. The theoretical yield of the acetal was 0.343 g, and the percent yield was 64.7%. The melting point of the acetal product was 57.8 degC. The low percent of product could have been caused by boiling away acetone during reflux, boiling away product because of its low mp (57.8), or mixture of product and hexane soaked up in cotton. Because the hydrobenzoin that reacted with the acetone to form the acetal was meso (1R,2S), the the hydrogens on the methyl groups of the acetal were diastereotopic; therefore, two methyl peaks were seen in the NMR for 2,2-dimethyl-1,3-dioxolane.

Conclusion:

In this lab, the synthesis of a carbonyl protecting group, dioxolane was introduced. The stereoselective reduction of benzyl using sodium borohydride was demonstrated in order to determine the identity of the diol hydrobenzoin. The 134.8 mp of hydrobenzoin determined it to be R,S stereochemistry, which is the meso configuration; therefore, the meso diol reacted with acetone to form the acetal 2,2-dimethyl-1,3-dioxolane with diastereotopic hydrogen on the methyl groups. The NMR further characterized the diastereotopic hydrogens by representing two different peaks for the different hydrogens on the two methyl groups.

Radical Chlorination

Chlorine has 4 possible carbons to bond to. When the products are analyzed, the most reactive hydrogens have the highest amound of isomers, and leave more easily. The 1,3-dichlorobutane isomer was the most common, forming almost 4 times as fast as the 1,4-dichlorobutane (C4 farthest from chlorine and least influenced by its electronegativity). The next most reactive hydrogens were located on carbon number 2, followed by those on carbon number 4, and then those on carbon number 1. Chlorine has a strong pull on electrons, so it increases the strength of the carbon-hydrogen bonds close to it. If bond strength increases, then relative reactivity decreases. This would have the most effect on the carbon-hydrogen bonds of carbon number 1 and carbon number 2 because they are closer to chlorine. Chlorine would have the slightest influence on carbon number 3 and carbon number 4 because they are farther from chlorine. Chlorine also causes steric issues with the structure of 1,1-dichlorobutane. Because there is a chlorine on carbon number 1, the development of a second carbon-chlorine bond is unlikely, which is represented in the GC as a low percentage. Free-radicals are most stable when the unpaired electron is accompanied by more than one alkyl group. The more alkyl groups attached to the carbon where the lone electron is, the more stable that free-radical. When the free-radical forms at carbon-3, it is located between two alkyl groups. When it forms on carbon number 4, it is only near one alkyl group. Therefore, the lone electron is found most frequently on carbon number 3 because it is more stable.

Chemiluminescence of Luminol

In this experiment, luminol was synthesized in order to perform a chemiluminescent (light emitting) reaction. In the first step of the reaction, triethylene glycol (TEG) was used as a solvent. Hydrazine was mixed with 3-nitrophthalic acid and heated in TEG. Because TEG has a high boiling point (~285 deg.C), the temperature was first raised to 100 deg.C to boil off water, and then raised to ~215 deg.C to drive dehydration of the liquid to completion. In the second step, 3-nitrophthalhydrazide underwent a reduction—the nitro group was reduced to an amino group. Sodium hydrosulfide was the reagent that caused the change. In step three, the energy for the generation of light for the luminol reaction came from luminol being activated with an oxidant. In this case, the oxidant activator was the mixture of 3M sodium hydroxide and hydrogen peroxide, in the presence of the catalyst potassium ferricyanide. The reaction of luminol and 3M sodium hydroxide formed a dianion, which reacted with the oxygen from hydrogen peroxide. The product lost a nitrogen, which caused the electrons to go from an excited state to ground state, and the energy was emitted as a photon of (bluish) light. The reaction is classified as exothermic. The chemiluminescent reaction was very successful resulting in a blue glow when luminol was mixed with the peroxide/iron solution; therefore, luminol was successfully synthesized. The crude product of luminol in the experiment weighed 0.136 g (7.67 x 10^-4 mol), which resulted in a percent yield of 81%. The loss of product can be concluded in different steps of the procedure. In step one, the solution boiled a little bit longer than expected and the precipitate collected by vacuum filtration was collected on filter paper in which some of the precipitate stuck to. In step two, the luminol crude product was also collected on filter paper; therefore, some of the product may have still been on the filter paper. Also, in the two vacuum filtrations, a small amount of product may have went through the filter. An IR, HNMR, and CNMR were provided by the instructor. According to the chemical formula, luminol has 4 double bond equivalents, which represent the aromatic ring. For the IR spectra, the peaks at 3300 and 3400 cm^-1 represent the amine (N-H) groups on the compound. The peaks from 1450 to 1600 cm^-1 represent the aromatic ring, and Benzene is at ~3050 cm^-1. The carbonyl group amide (O=C-N) typically shows a peak at 1690 cm^-1; however, the spectra shows the peak to be ~1670 cm^-1. The HNMR spectra has peaks between 6.5 and 8 ppm, which represents the aromatic ring. The CNMR spectra has peaks ranging from 110 to 160 ppm. The aromatic range for CNMR is 110-170 ppm. The amide peak is usually in a range from 165-175; therefore, the peak at ~162 ppm is probably the amide carbon. The range from 100-150 also represents sp2 hybridized carbons. The CNMR shows 8 carbon signals that coordinate with 8 carbons on the luminol compound.

Conclusion:

In this experiment, the compound luminol was successfully synthesized and underwent a chemiluminescent reaction. The light emitting reaction was also successful, in which a photon of blue light was emitted when luminol/sodium hydroxide solution was combined with the potassium ferricyanide/hydrogen peroxide solution.