Post-Lab Report 6 - Nicole Archer PDF

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Nitration of Methyl Benzoate...

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Nitration of Methyl Benzoate Nicole Archer 05 October 2020 CHM2211L.904 Jason Cruce

Introduction Aromatic compounds are cyclic compounds that must abide by certain rules to be considered aromatic. First, the compound must be cyclic. Any indication of lone pairs that do not participate in the conjugated pi system will declassify the reaction as cyclic, as it does not follow rules of planarity. Second, the compound must abide by a [4n+2] rule in relation to electrons.3 Therefore, compounds with 2, 6, 10 and so on electrons will classify as aromatic. Aromaticity also asks that the bonds in participating in the ring be conjugated.3 Any indication that the compound lacks conjugation will result in the declassification of aromatic. Aromatic compounds are known to have superb stability in comparison to the alkene family. The conjugated pi systems and delocalization of electrons allows for resonance structures to form the most stable formation.3 Because of the stability and properties of aromatic compounds, it allows for a key reaction or organic chemistry to take place – the electrophilic aromatic substitution reaction.2 These reactions are generally aided by the addition of a Lewis acid catalyst2, and in this case, that is concentrated nitric and sulfuric acid.1 In this reaction, a carbon-hydrogen bond is broken and a carbon-electrophile bond is formed. In the first step of this reaction, electrons in one of the conjugated bonds at the meta position attacks the electrophilic reagent (nitronium ion), which forms a bond with the electrophile and aromatic ring. This intermediate forms a positively charged arenium ion, which then later gets deprotonated to produce a substituted aromatic compound. There are patterns in which substituents of the reaction are able to direct where the substitution will be located, giving substitution at different positions labeled ortho (1,2), para (1,4) and meta (1,3).4 Certain directors may be labeled as either an activating or deactivating group, which is either increase the rate of electrophilic aromatic substitution or decrease it,

respectively.4 Deactivating groups are often deemed as those that coincide with meta-directors while on the flip side, activating groups are composed of the ortho- and para- directors. Some of the more common activating groups include hydroxyl, alkoxy, amino, alkyl and thio functional groups that function as ortho and para directors. Deactivating groups of the ortho and para directors include halogens such as fluorine, chlorine, bromide and iodine. On the contrary, deactivating groups of the meta directors can include functional groups like nitro, carbonyls, cyano and sulfonyl.4

Main Reaction

Side Reactions

Experimental Add 0.3g Methyl Benzoate and 0.6 mL Sulfuric Acid to a test tube. Swirl. Cool to 0C

In a separate tube, combine 0.2 mL Sulfuric Acid and 0.2 mL Nitric Acid. Use a Pasteur pipet to add into previous solution. Place reaction mixture over ice and continue mixing with stirring rod

Following the completion addition of Sulfuric Acid and Nitric Acid, swirl for 2 additional minutes while solution is over ice. Remove from ice. Cool to room temperature for a total of 15 minutes

Filter product again, weigh, calculate melting point and % yield. Obtain 1H NMR and 13C NMR

Use an equal weight of methanol to purify product further in separate test tube containing product.

Use vacuum filtration to isolate solidified product. Add 3g crushed ice to a 50 mL beaker and carefully pour the reaction over it. Use cold water to wash the mixture and then with 0.5 mL ice cold methanol following the wash with water.

Table of Chemicals Chemical

Formula

Molar Mass 136.05 g/mol

Density

Methyl Benzoate

C8H8O2

Clear to light yellow liquid 3-nitro methylbenzoate

C8H7NO4

181.15 g/mol

Beige Crystalline Powder Sulfuric Acid

H2SO4

Clear to Yellow Liquid Nitric Acid

Clear to Yellow Liquid Methanol

Clear Liquid

Melting Point -12.2C

Boiling Point 150C

1.3 g/cm3

78-80C

279C

98.07 g/mol

1.84 g/cm3

10C

290-338C

HNO3

63.01 g/mol

1.4 g/cm3

-42C

86C

CH4O

32.04 g /mol

7910 g/cm3

-98C

64.7C at 760 mmHg

1.1 g/cm3

Results Figure 1: 1H NMR Spectrum of 3-nitro methylbenzoate

Figure 2: Theoretical 1H NMR Spectrum of 3-nitro methylbenzoate

Figure 3: 13C NMR Spectrum of 3-nitro methylbenzoate

Figure 4: Theoretical 13C NMR Spectrum of 3-nitro methylbenzoate

Starting Mass (Methyl Benzoate) Final Mass of 3-nitro methylbenzoate Melting Point of 3-nitro methylbenzoate

0.3 g 0.256 g

*Experimental

78-80C

*Theoretical 78-80C Table 1: Table representative of the qualitative data analyzed throughout the course of the experiment including starting mass of Methyl Benzoate and final mass/melting point of 3-Nitromethyl Benzoate

Percent Yield Limiting Reagent 0.3 g C8H8O2

x

1mol C 8 H 7 NO 4 1 mol C 8 H 8 O2 x = 0.0022mol 3 − Nitro methyl b enzoate 1mol C 8 H 802 136.05 g C 8 H 8 O 2

(Limiting) 0.2 mL HNO3 x

1.513 g HNO 3 1 mol HNO 3 1mol C 8 H 7 NO 4 x x =¿ 0.004 mol 3-nitro 1mol HNO 3 1 mL HNO 3 63.01 g HNO3

methylbenzoate Theoretical Yield 0.3 g C8H8O2

x

1mol C 8 H 7 NO 4 181.15 g C 8 H 7 NO 4 1 mol C 8 H 8 O2 x x =¿ 1 mol C 8 H 7 NO 4 1mol C 8 H 802 136.05 g C 8 H 8 O 2

0.4 g 3-nitro

methylbenzoate Actual Yield

0.256 g 3−Nitromethyl Benzoate x 100 0.4 g 3−Nitromethyl Benzoate

= 64%

Discussion The melting point of 3-nitro methylbenzoate found at the conclusion of the experiment was deemed to be 78-80C. The melting point found in literature values is also 78-80C, which coincides identically with that found in the experiment. The melting point derived from the experiment proves the identity of the product to be 3-nitro methylbenzoate with complete confidence, as no appearance of contamination were found in the final product.

The percent yield of 3-nitro methylbenzoate was calculated to be 64% after the final product was obtained and weighed to be 0.265 g. This low percentage yield can be attributed to a variety of errors, including incomplete transfer of product to Hirsch funnel, presence of side reactions occurring leading to the formation of o-nitromethyl benzoate, p-nitromethyl benzoate or 3,5-dinitromethylbenzoate, or incomplete drying of the final crude product. Although the percent yield was deemed low, the yield falling over 50% still allows one to assume the experiment was relatively successful in the formation of 3-nitro methylbenzoate. The 1H NMR spectrum of the final product was produced at the end of the experiment to further conclude the identity of the product as 3-nitro methylbenzoate. A theoretical 1H NMR spectrum is given in Figure 2 above, with characteristic peaks lying at 3.9 PPM (singlet), 7.7 PPM (triplet), 8.3 PPM (doublet) and 8.6 PPM (singlet). These peaks are indicative of proton number(s) 1, 4, 3 and 5, and 6, respectively. The four peaks characterized and labeled according to the protons attached to 3-nitro methylbenzoate were also found on the 1H NMR obtained experimentally, found in Figure 1. Appropriate peaks, including the singlet at around 3.9 PPM and peaks lying close to 7.4 PPM (along with other attached peaks) allow for the confirmation that the final product was transformed to the desired, 3-nitro methylbenzoate structure.

Conclusion By the end of the experiment, the theories and methods relating to nitration should have been demonstrated through the nitration of 3-nitro methylbenzoate from Methyl Benzoate. Methods also relating to 1H NMR, percent yield, and melting point to determine the final product were also employed in the determination of the final products identity. Overall, with a melting point coinciding exactly to literature values, an experimental 1H NMR spectrum

correlating to theoretical with minor imprecisions, and a percent yield over 60%, this experiment was able to successfully use methods relating to the nitration reaction in the formation of 3-nitro methylbenzoate.

References [1] Weldegirma, S. Experimental Organic Chemistry Laboratory Manual, 8th ed.; Procopy Inc: Tampa, Florida, 2019-2020

[2] Alex, et al. “Electrophilic Aromatic Substitution: The Six Key Reactions.” Master Organic Chemistry, 30 Sept. 2020, www.masterorganicchemistry.com/2017/07/11/electrophilicaromatic-substitution-introduction/.

[3] Paul, et al. “Rules for Aromaticity: The 4 Key Factors.” Master Organic Chemistry, 5 Oct. 2020, www.masterorganicchemistry.com/2017/02/23/rules-for-aromaticity/.

[4] Matthew, et al. “Ortho-, Para- and Meta- Directors in Electrophilic Aromatic Substitution.” Master Organic Chemistry, 30 Jan. 2020, www.masterorganicchemistry.com/2018/01/29/ortho-para-and-meta-directors-inelectrophilic-aromatic-substitution/....