Question

CONCEPT QUESTIONS (1) Instead of dropwise addition of anthranilic acid and isoamyl nitrite to the reaction vessel, a student adds all of their anthranilic acid and isoamyl nitrite in two portions. The remaining portion of the experiment is completed, and the student takes TH NMR and C NMR spectra of their final solid, as shown below. "H NMR Spectrum of Sample (300 MH2, DMSO, 25 °C) PPM 2M 1H1M INC NMR Spectrum of Sample (100 MHz, DMSO, 25°C) 2244 PPM The 'H NMR and 13C NMR spectra of pure 1,2,3,4-tetraphenylnapthalene are provided below. *H NMR Spectrum of Pure Product (300 MHz, DMSO, 25 °C) PPM 22H 13C NMR Spectrum of Pure Product (100 MHz, DMSO, 25 °C) 150 130 120 PPM (a) Propose a structure of the impurity in the student's sample, and explain with less than 20 words how the rate of addition of anthranilic acid and isoamyl nitrite may heighten the formation of the impurity. (b) Based on the spectral information provided, what is the ratio of 1,2,3,4-tetraphenylnapthalene to the impurity in the sample? (c) Explain why the impurity was not removed with the rotary evaporator. (d) Explain why the impurity was not removed during trituration.

Answer 1

9 h I we compare pure product WMR of the crude NMR after reaction we could see the two extra peaks in the aromatic region, at 8.2 ppm in f 8.4 ppm doublet which indicates two types of aromatic signles. The simpurity, might be Biphenylene impurity when we add both the reacts ut together higher the concentration of benzyne intermediate leads to formation of this biphenylene impurity. .ph imponity a produnt. It we compare these two structures impurity has & protons. & due to symmetry it shows to two distinct peats in NMR. Product has total 24 protows. If we consider 24 protons for impurity that means tread to head we had only 2 protons for 44 for 50% impurity so there is only 20% impurity present in mixture - Impurity also has to high bolling point like desired product It is not rolatile so it will not get remored cepon. distillation on rolavapar. d) Impurity is not reactive to woods any reagent we use for tiltration as product aso will come with impurity.