Nitrogen containing compounds. Nitrocompounds . Amines. Dia zo- and azocompounds .

1. Nitrogen containing compounds. Nitrocompounds. Amines.Diazo- andazocompounds. Prepared by ass. Medvid I.I., ass. Burmas N.I.

2. Outline • Nitroderivates of hydrocarbons. • The methods of extraction of nitroalkanes. • Chemical properties of nitroalkanes. • The aromatic nitrocompounds. • Amines. • Isomery of amines. • Structure and bonding of amines. • Physical propertiesof amines. • The methods of extraction of amines. • Chemical properties of amines. • Synthetically useful transformations involving aryl diazonium ions. • The medico-biological importance of amines. • Aminoalcohols. • The methods of extraction of aminoalcohols. • Chemical properties of aminoalcohols. • Arylamines. • The methods of extraction of aromatic amines. • Physical properties of aromatic amines • Comparative structure of aromatic and aliphatic amines • Sulphanilicacid • The synthesis of streptocide • Sulphanylamidic preparations • Medicinal preparations (derivates of p-aminobenzoic acid (pABA). • Diazocompounds • The methods of extraction of aromatic diazocompounds • Chemical properties aromatic diazocompounds • Azocompounds • The methods of extraction of aromatic azocompounds. • Chemical properties of aromatic azocompounds • Physical bases of theory of colouration • Azo-dyes.

3. 1. Nitroderivates of hydrocarbons Nitrocompounds are the derivatives of hydrocarbons which contain one or several groups –NO2 in their molecule. Nitroalkanes are poisonous colourless or yellowish liquids with good smell. They are not dissoluble in water but are dissoluble in organic solvents. The names of nitrocompound are formed by adding prefix nitro- to the names of hydrocarbons. The isomery of nitrocompound is specified by different structure of carbon chain and different location of group –NO2 in the molecule.

4. 2. The methods of extraction of nitroalkanes 1. Nitration of alkanes CH3−CH3 + HNO3 → CH3−CH2−NO2 + H2O 2. The reaction of halogenalkanes with salts of HNO2 CH3−CH2−I + NaNO2 → CH3−CH2−NO2 + NaI 3. Oxidation of amines

5. 3.Chemical properties of nitroalkanes Chemical properties of nitroalkanes are specified by the presence of group –NO2 in the structure of the molecule. • Reaction with HNO2 • Reaction with aldehydes and ketones 3. Reduction of nitroalkanes. In the result of this reaction amines form (catalyst is SnCl2) CH3−CH2−NO2 + 3H2 → CH3−CH2−NH2 + 2H2O

7. 4.The aromatic nitrocompounds The simplest aromatic nitro compound, having the molecular formula C6H5NO2. Nitrobenzene, also known as nitrobenzol or oil of mirbane, is an organic compound with the chemical formula C6H5NO2. Nitrobenzene is a water-insoluble oil which exhibits a pale yellow to yellow-brown coloration in liquid form (at room temperature and pressure) with an almond-like odor. When frozen, it appears as a greenish-yellow crystal. Although occasionally used as a flavoring or perfume additive, nitrobenzene is highly toxic in large quantities and is mainly produced as a precursor to aniline. In the laboratory, it is occasionally used as a solvent, especially for electrophilic reagents.

8. Properties of nitrobenzene: 1. Production Nitrobenzene is prepared by nitration of benzene with a mixture of concentrated sulfuric acid, water, and nitric acid, called "mixed acid." Its production is one of the most dangerous processes conducted in the chemical industry because of the exothermicity of the reaction (ΔH = −117 kJ/mol). There were four producers of nitrobenzene in the United States in 1991. 2. Mechanism of nitration The reaction pathway entails formation of an adduct between the Lewis acidic nitronium ion, NO2+, and benzene. The nitronium ion is generated in situ via the reaction of nitric acid and an acidic dehydration agent, typically sulfuric acid: HNO3 + H+ ⇌ NO2+ + H2O

9. Zinin’s reaction:

12. 3. Uses Approximately 95% of nitrobenzene is consumed in the production of aniline. 4. Specialized applications More specialized applications include the use of nitrobenzene as a precursor to rubber chemicals, pesticides, dyes, explosives, and pharmaceuticals. Nitrobenzene is also used in shoe and floor polishes, leather dressings, paint solvents, and other materials to mask unpleasant odors. Redistilled, as oil of mirbane, nitrobenzene has been used as an inexpensive perfume for soaps. A significant merchant market for nitrobenzene is its use in the production of the analgesic paracetamol (also known as acetaminophen) (Mannsville 1991). Nitrobenzene is also used in Kerr cells, as it has an unusually large Kerr constant.

13. 5. Organic reactions Aside from its conversion to aniline, nitrobenzene is readily converted to related derivatives such as azobenzene, nitrosobenzene, and phenylhydroxylamine. The nitro- group is deactivating, thus substitution tends to occur at the meta-position. 6. Safety Nitrobenzene is highly toxic (TLV 5 mg/m3) and readily absorbed through the skin. Although nitrobenzene is not currently known to be a carcinogen, prolonged exposure may cause serious damage to the central nervous system, impair vision, cause liver or kidney damage, anemia and lung irritation. Inhalation of fumes may induce headache, nausea, fatigue, dizziness, cyanosis, weakness in the arms and legs, and in rare cases may be fatal. The oil is readily absorbed through the skin and may increase heart rate, cause convulsions or rarely death. Ingestion may similarly cause headaches, dizziness, nausea, vomiting and gastrointestinal irritation.

14. 5. Amines Amines are the derivatives of ammonium. In its molecules atoms of hydrogen (1,2 or 3) are substituted to atoms of hydrocarbon radicals. The names of amines are formed by adding suffix -amine to the names of hydrocarbon radical.

15. 6. Isomery of amines Isomery of amines is specified by different structure of hydrocarbon radicals, different location of aminogroup and methamery. Methamery is a phenomenon when amines have the same molecular formula but can be primary, secondary or tertiary.

16. Aniline is the parent IUPAC name for amino-substituted derivatives of benzene. Substituted derivatives of aniline are numbered beginning at the carbon that bears the amino group. Substituents are listed in alphabetical order, and the direction of numbering is governed by the usual “first point of difference” rule. Arylamines may also be named as arenamines. Thus, benzenamine is an alternative, but rarely used, name for aniline. Compounds with two amino groups are named by adding the suffix -diamine to the name of the corresponding alkane or arene. The final -e of the parent hydrocarbon is retained.

17. Amino groups rank rather low in seniority when the parent compound is identified for naming purposes. Hydroxyl groups and carbonyl groups outrank amino groups. In these cases, the amino group is named as a substituent. Secondary and tertiary amines are named as N-substituted derivatives of primary amines. The parent primary amine is taken to be the one with the longest carbon chain. The prefix N- is added as a locant to identify substituents on the amino nitrogen as needed.

18. 7. Structure and bonding of amines Alkylamines: As shown in Figure.1 methylamine, like ammonia, has a pyramidal arrangement of bonds to nitrogen. Its H-N-H angles (106°) are slightly smaller than the tetrahedral value of 109.5°, whereas the C-N-H angle (112°) is slightly larger. The C-N bond distance of 147 pm lies between typical C-C bond distances in alkanes (153 pm) and C-O bond distances in alcohols (143 pm). An orbital hybridization description of bonding in methylamine is shown in Figure. 2. Nitrogen and carbon are both sp3-hybridized and are joined by a σ bond. Figure.1 Methylamine

19. Arylamines: Aniline, like alkylamines, has a pyramidal arrangement of bonds around nitrogen, but its pyramid is somewhat shallower. One measure of the extent of this flattening is given by the angle between the carbon–nitrogen bond and the bisector of the H-N-H angle. For sp3-hybridized nitrogen, this angle (not the same as the C-N-H bond angle) is 125°, and the measured angles in simple alkylamines are close to that. The corresponding angle for sp2 hybridization at nitrogen with a planar arrangement of bonds, as in amides, for example, is 180°. The measured value for this angle in aniline is 142.5°, suggesting a hybridization somewhat closer to sp3 than to sp2. Figure.2

20. The corresponding resonance description shows the delocalization of the nitrogen lone-pair electrons in terms of contributions from dipolar structures.

21. 8.Physical propertiesof amines We have often seen that the polar nature of a substance can affect physical properties such as boiling point. This is true for amines, which are more polar than alkanes but less polar than alcohols. For similarly constituted compounds, alkylamines have boiling points higher than those of alkanes but lower than those of alcohols. Dipole–dipole interactions, especially hydrogen bonding, are present in amines but absent in alkanes. The less polar nature of amines as compared with alcohols, however, makes these intermolecular forces weaker in amines than in alcohols. Among isomeric amines, primary amines have the highest boiling points, and tertiary amines the lowest.

22. Primary and secondary amines can participate in intermolecular hydrogen bonding, but tertiary amines cannot. Amines that have fewer than six or seven carbon atoms are soluble in water. All amines, even tertiary amines, can act as proton acceptors in hydrogen bonding to water molecules. The simplest arylamine, aniline, is a liquid at room temperature and has a boiling point of 184°C. Almost all other arylamines have higher boiling points. Aniline is only slightly soluble in water (3 g/100 mL). Substituted derivatives of aniline tend to be even less water-soluble.

23. 9. The methods of extraction of amines

26. Hoffman reaction: NH3 NH3 + CH3I → [CH3NH3+]I− ↔ CH3NH2 + NH4I NH3 CH3NH2 + CH3I → [(CH3)2NH2+]I− ↔ (CH3)2NH + NH4I NH3 (CH3)2NH + CH3I → [(CH3)3NH+]I− ↔ (CH3)3N + NH4I NH3 (CH3)3N + CH3I → [(CH3)4N+]I− Gabriele synthesis:

28. 10. Chemical properties of amines

29. Nitrosation of arylamines We learned in the preceding section that different reactions are observed when the various classes of alkylamines—primary, secondary, and tertiary—react with nitrosating agents.

30. Primary arylamines, like primary alkylamines, form diazonium ion salts on nitrosation. Aryl diazonium ions are considerably more stable than their alkyl counterparts. Whereas alkyl diazonium ions decompose under the conditions of their formation, aryl diazonium salts are stable enough to be stored in aqueous solution at 0–5°C for reasonable periods of time. Loss of nitrogen from an aryl diazonium ion generates an unstable aryl cation and is much slower than loss of nitrogen from an alkyl diazonium ion.

32. Reaction with acids: CH3CH2NH2 + HCl → [CH3CH2NH3]+Cl− Reaction with halogenalkanes: CH3CH2NH2 + CH3−I → [CH3CH2NH3]+I− → CH3CH2NHCH3 + HI Reaction with functional derivatives of carboxylic acids. In the result of these reactions amides form. Reaction with HNO2 Isonitrylic reaction Oxidation C2H5NH2 + O3 → C2H5NO2 + H2O

33. 11. Synthetically useful transformations involving aryl diazonium ions

37. 12.The medico-biological importance of amines • Methylamine CH3NH2. It is a gas with the smell of ammonium. Methylamine is used in the production of medicines, dyes, insecticides and fungicides. • Putrescin NH2CH2CH2CH2CH2NH2(tetramethylendiamine). It is crystal solid. It is formed in the process of rotting of corpses. In the human organism it is used for synthesis of biologically active polyamines which take part in the biosynthesis of DNA and RNA. • Cadaverine NH2CH2CH2CH2CH2CH2NH2 (pentamethylendiamine). It is liquid. It is formed in the process of rotting of corpses like putrescin. • Aniline C6H5NH2. It is colourless liquid with peculiar smell. It is poisonous. It is used in the process of synthesis of dyes, medicines, plastic materials. • Phenamine C6H5CH2CH(NH2)CH3 (1-phenylpropanamine-2). It is white crystal solid. It is used as stimulator of CNS.

38. 13. Aminoalcohols Aminoalcohols are the derivatives of hydrocarbons which contain aminogroup in their molecule. For aminoalcohols it is used the nomenclature according to which the location of aminogroup is denoted by number or Greek letter. Isomery of aminoalcohols is similar to isomery of disubstituted hydrocarbons. 2-aminoethanol or β-aminoethyl alkohol 2-N-methylaminoethanol

39. 14. The methods of extraction of aminoalcohols: • Joining of ammonium or amines to α-oxides • Reduction of nitroalcohols • Reaction of halogenalcohols with ammonium or amines

40. 15. Chemical properties of aminoalcohols Chemical properties of aminoalcohols are specified by the presence of –OH and aminogroups in the structure of its molecules. Aminoalcohols have basic reaction. 1. Reaction with acids: 2.Reaction with SOCl2:

41. 16. Arylamines Arylamines are the derivatives of ammonium. In its molecule one, two or three hydrogen atoms are substituted to aromatic radicals. The names of arylamines depend on the presence of aromatic radicals and their locations.

42. Arylamines: Aniline, like alkylamines, has a pyramidal arrangement of bonds around nitrogen, but its pyramid is somewhat shallower. One measure of the extent of this flattening is given by the angle between the carbon–nitrogen bond and the bisector of the H-N-H angle.

43. For sp³-hybridized nitrogen, this angle (not the same as the C-N-H bond angle) is 125°, and the measured angles in simple alkylamines are close to that. The corresponding angle for sp² hybridization at nitrogen with a planar arrangement of bonds, as in amides, for example, is 180°. The measured value for this angle in aniline is 142.5°, suggesting a hybridization somewhat closer to sp³ than to sp². The structure of aniline reflects a compromise between two modes of binding the nitrogen lone pair (Figure 22.3). FIGURE 22.3 Electrostatic potential maps of the aniline in which the geometry at nitrogen is (a) nonplanar and (b) planar.

44. The electrons are more strongly attracted to nitrogen when they are in an orbital with some s character—an sp³-hybridized orbital, for example— than when they are in a p orbital. On the other hand, delocalization of these electrons into the aromatic π system is better achieved if they occupy a p orbital. A p orbital of nitrogen is better aligned for overlap with the p orbitals of the benzene ring to forman extended π system than is an sp³-hybridized orbital. As a result of these two opposing forces, nitrogen adopts an orbital hybridization that is between sp³ and sp². The corresponding resonance description shows the delocalization of the nitrogen lone-pair electrons in terms of contributions from dipolar structures. In the nonplanar geometry, the unshared pair occupies an sp³ hybrid orbital of nitrogen. The region of highest electron density in (a) is associated with nitrogen. In the planar geometry, nitrogen is sp²-hybridized and the electron pair is delocalized between a p orbital of nitrogen and the π system of the ring. The region of highest electron density in (b) encompasses both the ring and nitrogen.

45. The actual structure combines features of both; nitrogen adopts a hybridization state between sp³ and sp². The orbital and resonance models for bonding in arylamines are simply alternative ways of describing the same phenomenon. Delocalization of the nitrogen lone pair decreases the electron density at nitrogen while increasing it in the π system of the aromatic ring. We’ve already seen one chemical consequence of this in the high level of reactivity of aniline in electrophilic aromatic substitution reaction. Other ways in which electron delocalization affects the properties of arylamines are described in later sections of this chapter.

46. The derivatives of toluene are called toluidines: o-toluidine m-toluidine p-toluidine benzylamine N-methylaniline

47. 2 H, pH= 7 2 H 2 H C H -NO C H -N=O C H -NH - OH C H -NH 6 5 2 6 5 6 5 6 5 2 -H O -H O 2 2 Nitrozo- N-Phenylhyd roxilaniline benzene 17. The methods of extraction of aromatic amines • Recovery of nitroarenes (Zinin reaction)

48. II. Reaction of halogenarenes with ammonium and amines.

49. III. Alkylation of primary aromatic amines

50. 18. Physical properties of aromatic amines Aromatic amines are colourless liquids or solids with peculiar smell. They can be oxidized by open air very easily. Aromatic amines are very toxic compounds. Hydrogen bonding significantly influences the properties of primary and secondary amines. Thus the boiling point of amines is higher than those of the corresponding phosphines, but generally lower than those of the corresponding alcohols. Thus methylamine and ethylamine are gases under standard conditions, whereas the corresponding methyl alcohol and ethyl alcohols are liquids. Gaseous amines possess a characteristic ammonia smell, liquid amines have a distinctive "fishy" smell. Also reflecting their ability to form hydrogen bonds, most aliphatic amines display some solubility in water. Solubility decreases with the increase in the number of carbon atoms. Aliphatic amines display significant solubility in organic solvents, especially polar organic solvents. Primary amines react with ketones such as acetone, and most amines are incompatible with chloroform and carbon tetrachloride. The aromatic amines, such as aniline, have their lone pair electrons conjugated into the benzene ring, thus their tendency to engage in hydrogen bonding is diminished. Their boiling points are high and their solubility in water low