Preparation OF P- Iodonitrobenzene PDF

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EXPERIMENT 3 PREPARATION OF P-IODONITROBENZENE

NAME: KAGISO B

SURNAME: MFANYANA

ID NUMBER: 201301326

LAB DAY: MONDAY

COURSE CODE: CHE334

TITTLE: PREPARATION OF P-IODONITROBENZENE AIM: To synthesize (using a diazotization reaction), purify and record the yield and melting point of p-Iodonitrobenzene

INTRODUCTION Benzenediazonium salts (ArN2+Y-) are very useful for the synthesis of compounds, such as iodoarenes (ArI) and arenenitriles (ArCN) that are not easily available from electrophilic aromatic substitution reactions. The diazonio group (N2+) is a “super” leaving group that makes the attached carbon very electrophilic and susceptible to nucleophilic attack. Thus, benzenediazonium salts can undergo a variety of nucleophilic aromatic substitution reactions by nucleophiles such as iodide ion (eq 1, Nu:- = I-). These reactions are irreversible due to the fact that the formed N2 gas rapidly bubbles out of solution.

The outer nitrogen atom of the diazonium salt is also an electrophilic site and can serve as the electrophilic atom in aromatic substitution reactions on activated benzene rings such as anilines and phenoxides. The diazonium salt is prepared using sodium nitrite and sulfuric acid from the corresponding aromatic amine in a process termed "diazotization" PhNH2 + NaNO2 + H2SO4

PhN2+HSO4- + 2H2O

In this experiment diazotization of p-nitroaniline was carried out and the resulting p-nitrobenzenediazonium salt solution was reacted with aqueous potassium iodide to form piodonitrobenzene.

APPARATUS 1. P-nitroaniline 2. 400ml beaker (2) 3. Sodium nitrite 4. Concentrated sulphuric acid 5. 25ml Erlenmeyer flask 6. Buchner funnel 7. Filter paper 8. Water bath 9. Hot plate 10. Isopropyl alcohol EXPERIMENTAL PROCEDURE p-nitroaniline was prepared by adding 2.0ml concentrated H2SO4 to a mixture of, 10g ice and 10ml water in 400ml beaker. This mixture was kept in ice bath to cool it to about 5oc and 1.25g of p-nitroaniline was slowly added to it and stirred to dissolve. A solution of 0.63g sodium nitrite dissolved in 5ml water was prepared and slowly added to the amine sulphate to diazotise it. The temperature while this procedure was being employed was kept below 10C at all times. A solution of 2.5g potassium iodide was then prepared in 15ml of water in another 400ml beaker. The diazonium salt solution was then slowly added to a solution of sodium. It was mixed well and the precipitated solid collected by suction filtration. The product was recrystallised in ethanol, dried in air, and the yield and melting point obtained. An IR spectrum was also obtained and all major peaks assigned. RESULTS AND ANALYSIS Product Weight: Weight of watch glass alone: 41.67g Weight of filter paper: 0.33g Weight of watch glass, filter paper and product: 43.43g Weight of product: 1.43g Melting Point: Melting point of product: 171-173oc

Theoretical Yield:

PhNH2 + NaNO2 + H2SO4

PhN2+HSO4- + 2H2O

KI

PhI + N2

1. Mr of p-nitroaniline: 138g/mol 2. Mr of p-Iodonitrobenzene: 249g/mol From equation: 1 mole of p-nitroaniline gives 1 mole of p-Iodonitrobenzene moles ( p−nitroaniline )=

1.25 g mass = =9.058∗10−3 mol Mr 138 gmol−1

−3 moles ( p−Iodonitrobenzene )=9.058∗10 mol

−3 −1 Theoretical mass(PhI )=moles∗Mr =( 9.058∗10 mol ) (249 gmol ) =2.26 g

% yield =

actual 1.43 g ∗100=63.4 % ∗100= 2.26 g Theoretical yield

IR Spectrum Table 1: Absorption peaks from the IR spectrum of p-Iodonitrobenzene Functional group (band) Peaks (cm-1) 3093.9 C–H stretch 1591.2 C–C stretch (in-ring) 1568.8 C–C stretch (in-ring) 1511.4 (C=C, aromatic) 1336 (CH2,CH3, bend) 838.2 C–H "oop" 736.1 C–I stretch or oop

DISCUSSION Aniline has a very reactive amino group (-NH2) which would be protonated (-NH3+) during the acidic conditions of nitration. When protonated, it deactivates the ring and leads to other reactions, such as oxidation or meta-nitration. This is why acetanilide is converted to pnitroaniline in two steps instead of converting aniline directly to p-nitroaniline in one step. The nitrating mixture is extremely reactive that is why in the first step of the synthesis, the nitrating mixture of concentrated acid is added slowly to acetanilide at cold temperatures. It is added slowly in order to keep the nitronium ion concentration low and avoid polynitration of the ring. Cold temperatures slow down the reaction rate and also help avoid over-nitration. At warmer temperatures, water replaces the diazonium -N2+ group and a phenol is formed. Looking at the IR spectrum of the product it can be said that all the conditions necessary for synthesis of piodonitrobenzene were met. The spectrum is exactly as those found in databases (spectrabase.com). The fingerprint regions match. The color of the product was dark brown and it had very high purity according to similarity of IR spectrum to standard spectrum. The percentage yield of the product was 63.4% and mass of 1.43g compared to a theoretical of 2.26g.. Its melting point was measured to range from 171 to 173OC and literature shows that piodonitrobenze has a melting point range of 172- 174OC (www.nist.gov). IR spectroscopy was then used to determine the various functional groups in the isolated p-iodonitrobenzene. The functional groups present include the aromatic alkene stretch at 1591.2 cm-1, allyl at 3093.9, the benzene C-H at 1511.4 and the fingerprint region. CONCLUSION The melting point was recorded as a range from 171-173oc and the percentage yield of the product was 63.4% (1.43g) compared to a theoretical yield of 2.26g. According to the IR spectrum the product was p-iodonitrobenzene as the spectrum matched those found in literature. REFERENCES Clarke H. T. and Kirner W. R., "Methyl red". Organic Syntheses.; Collective Volume, 1, p. 374 Hartwell J. L. and Louis F. Fieser. "Coupling of o-tolidine and Chicago acid". Organic Syntheses.; Collective Volume, 2, p. 145 Klaus H., Peter M., Wolfgang R., Roderich R., Klaus K., Aloys E., (2005). "Azo Dyes". Ullmann's Encyclopedia of Industrial Chemistry. Ullmann’s Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a03_245 Smith J., Michael B., March J., (2007), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (6th ed.), New York: Wiley-Interscience https://spectrabase.com/spectrum/9PnXWxJr1k accessed 17 february 2019 http://www.nist.gov/srd/nist1a.cfm MSDS OF P-IODONITROBENZENE

GHS Hazard Statements Aggregated GHS information provided by 26 companies from 3 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies. H302 (100%): Harmful if swallowed [Warning Acute toxicity, oral] H312 (100%): Harmful in contact with skin [Warning Acute toxicity, dermal] H315 (100%): Causes skin irritation [Warning Skin corrosion/irritation] H319 (100%): Causes serious eye irritation [Warning Serious eye damage/eye irritation] H332 (100%): Harmful if inhaled [Warning Acute toxicity, inhalation] H335 (96.15%): May cause respiratory irritation [Warning Specific target organ toxicity, single exposure; Respiratory tract irritation] Information may vary between notifications depending on impurities, additives, and other factors. The percentage value in parenthesis indicates the notified classification ratio from companies that provide hazard codes. Only hazard codes with percentage values above 10% are shown.

Exercise

1. The diazonium coupling is an electrophilic aromatic substitution reaction. Give a mechanism that clearly indicates this fact.

2. How would you synthesize Orange II from benzene and β-naphthol?

3. Assign the following resonance in the 1H NMR spectrum of phenyl azo-β-naphthol: 6.88, 8.58 and 16.26ppm

16.26ppm – NH 8.58ppm – 2H 6.88ppm – 1H

4. Assign the following in the IR spectrum: 1616 and 1626 cm-1

1616cm-1 – (C=C, aromatic) 1626cm-1 – (C=C, alkene)...