Theme: Alcohols. Phenols. Ethers.

1. LECTURE № 6 Theme: Alcohols. Phenols. Ethers. associate. prof. Ye. B. Dmukhalska, assistant. I.I. Medvid

2. Plane. Alcohols: Classification, nomenclature. The methods of extraction of monohydroxylalcohols. Monohydric alcohols:classification, isomery, physical, chemical properties of monohydroxyl alcohols. Di-, tri- and polyhydroxyl alcohols. Thioalcohols. Ethers (simple ethers). Enols. Aminoalcohols. The methods of extraction of mononuclear phenols Mononuclear phenols: the nomenclature, isomerism, physical, chemical properties Di-, tri- and polynuclear phenols: Chemical properties Aminophenols Aromatic carboxylic acids

3. Classificationofalcohols. All alcohols, а principle, can be divided into two broad categories i.е. aliphatic alcohols and aromatic alcohols. 1. Aliphatic alcohols. Alcohols in which the hydroxyl group is linked an aliphatic carbon chain are called aliphatic alcohols. For example, Methyl alcohol Ethyl alcohol Isopropyl alcohol Methanol Ethanol 2-Propanol

4. 2. Aromatic alcohols. Alcohols in which the hydroxyl group is present in the side chain of an aromatic hydrocarbon are called aromatic For example. phenylmethanol 2-phenylethanol (benzyl alcohol) (-phenylethyl alcohol) Alcohols are further classified as monohydric, dihydric, trihydric and роlyhydric according as their molecules contain one, two, three, or many hydroxyl groups respectively. For ехаmрlе, Ethyl alcohol 1,2-Ethanediol 1,2,3-propanetriol (Monohydric) (Dihydric) (Trihydric)

5. Тhe alkyl alcohol system. In this system of common nomenclature, the name of an alcohol is derived by combining the name of the alkyl group with the word alcohol. The names are mitten as two words. n-butyl alcohol isobutyl alcohol tret-butyl alcohol II. In this common system, the position of an additional substituent is indicated by use of the Greek alphabet rather than by numbers. -chloroethyl alcohol -bromobutyl alcohol

6. Any simple radical that has а common name may be used in the alkyl alcohol system, with one important exception. The grouping С6Н5 - has the special name phenyl, but the compound C6H5OH is phenol, not phenyl alcohol. phenol Substituted phenols are named as derivatives of the parent compound phenol. The reason for this difference is historical and arose from the fact that phenol and its derivatives have many chemical properties that are very different from those of alkyl alcohols. However, phenyl substituted alkyl alcohols are normal alcohols and often have common names. Examples are: phenylmethanol 2-phenylethanol (benzyl alcohol)(-phenylethyl alcohol)

7. III. The carbinol system. In this system, the simplest alcohol, СН3ОН, is called carbinol. More complex alcohols are named as alkyl substituted carbinols. The names are written as one word. butylmethylcarbinol triethylcarbinol phenilcarbinol The number of carbons attached to the carbinol carbon distinguishes primary, secondary, and tertiary carbinols. As in the case of the alkyl halides, this classification is useful because the different types of alcohols show important differences in reactivity under given conditions. The carbinol system of nomenclature has been falling into disuse in recent years. However, it is found extensively in the older organic chemical literature.

8. Polyhydroxy alcohols: An alcohol in which two hydroxyl groups are present is named as а diol, one containing three hydroxyl groups is named as а triol, and so on. In these names for diols, triols, and so forth, the final –е of the parent alkane name is retained for pronunciation reasons. 1,2-Ethanediol 1,2-propanediol 1,2,3-propanetriol

9. Classification of monohydric alcohols Monohydroxy alcohols are hydrocarbon derivatives which contain only one group –OH connected with sp³-hybridizated carbon atom. The general formula of monohydroxy alcohols is: The names of monohydroxy alcohols are the names of the same hydrocarbons with added prefix –ol.

11. Classification of monohydric alcohols. As already mentioned, alcohols containing one ОН group per molecule are called monohydric alcohols. These are further classified as primary (1'), secondary (2'), and tertiary (3') according as the ОН group is attached to primary, secondary and tertiary carbon atoms respectively. For example: Ethanol Isopropyl alcohol 2-Methylpropanane-2-ol Primary alcohol Secondary alcohol Tertiary alcohol

12. Isomery of monohydroxyl alcohols Monohydroxyl alcohols are characterized by structural, geometrical and optical isomery. Structural isomery depends on different structure of carbon chain and different locations of –OH group. For unsaturated monohydroxyl alcohols structural isomery depends on different locations of double bond too.

13. Only unsaturated monohydroxyl alcohols are characterized by geometrical isomery. Optical isomery is characteristic for alcohols which have asymmetric carbon atom in their structure.

14. The methods of extraction of monohydroxyl alcohols Alcohols can be obtained from many other classes of compounds. Preparations from alkyl halides and from hydrocarbons will be discussed in this section. The following important ways of prераring alcohols will be discussed later, as reactions of the appropriate functional groups. Hydrolysis of halogenderivatives of hydrocarbons by heating: CH3−CH2−Cl + NaOH → CH3−CH2−OH + NaCl 2. Hydrogenation of alkenes. This reaction runs by Markovnikov rule.

15. 3. Reduction of carbonyl compounds (aldehydes, ketones, carboxylic acids, complex ethers):

16. 1. Alcohols have weak acidic and weak alkaline properties. They can react with alkaline metals like acids and form alkoxides: 2CH3CH2OH + 2Na → 2CH3CH2ONa + H2↑ 2CH3CH2ONa + H2O ↔ CH3CH2OH + NaOH 2. Alcohols can react with mineral and organic acids (complex ethers form) like alkalis: CH3CH2OH + HONO2 ↔ CH3CH2ONO2 + HOH 3. Dehydration of alcohols. There are 2 types of dehydration: a) Dehydration between 2 molecules:

17. b) Dehydration in the molecule (intramolecular dehydration): 4. Reaction with HI, HCl, HBr: CH3CH2OH + HI → CH3CH2I + H2O 5. Oxidation

18. Primary alcohol aldehyde = carboxylic acid Secondary alcohol = ketone Tertiary alcohol = no reaction The general reaction for the oxidation of а primary alcohol is Alcohol Aldehyde Carboxylic acid In this equation, the symbol [O] represents the mild oxidizing agent. The immediate product of the oxidation of а primary alcohol is an aldehyde. Because aldehydes themselves are readily oxidized by the same oxidizing agents that oxidize alcohols, aldehydes are further converted to carboxylic acids. А specific example of а primary alcohol oxidation reaction is

19. The three classes of alcohols behave differently toward mild oxidizing agents. The general reaction for the oxidation of а secondary alcohol is As with primary alcohols, oxidation involves the removal of two hydrogen atoms. Unlike aldehydes, ketones are resistant to further oxidation. А specific example of the oxidation of а secondary alcohol is Alcohol Ketone

20. Tertiary alcohols do not undergo oxidation with mild oxidizing agents. This is because they do not have hydrogen on the -ОН-bearing carbon atom. To determine any alcohol (which contain fragment in the mixture of compounds it is needed to use iodoform test. As the result yellow precipitate forms.

25. Di-, tri- and polyhydroxyl alcohols Dihydroxyl alcohols contain two groups –OH in the molecule. They are called diols. There are several types of diols. 1. α-diols (groups –OH are situated near neighboring carbon atoms in 1,2-locations); 2. β-diols (groups –OH are situated in 1,3-locations); 3. γ-diols (groups –OH are situated in 1,4-locations) etc.

26. Trihydroxyl alcohols contain three groups –OH in the molecule. They are called triols. The representative is glycerin:

27. . To extract glycerin it is necessary to use next reaction:

28. b) Chemical properties of di-, tri- and polihydroxyl alcohols Reaction with alkaline metals 2. Reaction with Cu(OH)2

29. 3. Reaction with HI, HCl, HBr: 4. Formation of simple and complex ethers (reaction with monohydroxy alcohols and organic acids):

30. 5. Reaction with mineral acids:

31. 6. Oxidation by KMnO4 7. Dehydration

32. 8. Polycondensation 9.Diols react intramolecularly to form cyclic ethers when a five-membered or sixmembered ring can result.

33. Thioalcohols Thioalcohols are compounds which contain aliphatic (CnH2n+1) and mercaptane (−SH) groups. Thiols are given substitutive IUPAC names by appending the suffix -thiol to the name of the corresponding alkane, numbering the chain in the direction that gives the lower locant to the carbon that bears the −SH group. The preparation of thiols involves nucleophilic substitution of the SN2 type on alkylhalides and uses the reagent thiourea as the source of sulfur.

34. Both steps can be carried out sequentially without isolating the isothiouronium salt.

35. Chemical properties of thiols: Thiols can react with ions of alkaline and heavy metals (this property of thiols is used in medicine at the poisoning by heavy metals): C2H5SH + NaOH → C2H5S−Na+ + H2O 2C2H5SH + Hg²+ → (C2H5S)2Hg + 2H+ 2. They can react with alkenes (peroxides are catalysts): 3. Reaction with organic acids:

36. 4. Oxidation To preperethioalcohols it is necessary to use next reactions: C2H5Cl + NaSH → C2H5SH + NaCl 2. C2H5OH + Na2S → C2H5SH + H2O

37. Ethers (simple ethers) The general formula of simple ethers is: R−O−R1 The radicals can be similar or different. Ethers are named, in substitutive IUPAC nomenclature, as alkoxy derivatives of alkanes. Functional class IUPAC names of ethers are derived by listing the two alkyl groups in the general structure ROR1 in alphabetical order as separate words, and then adding the word “ether” at the end. When both alkyl groups are the same, the prefix di- precedes the name of the alkyl group.

38. Physical properties of ethers It is instructive to compare the physical properties of ethers with alkanes and alcohols. With respect to boiling point, ethers resemble alkanes more than alcohols. With respect to solubility in water the reverse is true; ethers resemble alcohols more than alkanes. In general, the boiling points of alcohols are unusually high because of hydrogen bonding. Attractive forces in the liquid phases of ethers and alkanes, which lack - OH groups and cannot form intermolecular hydrogen bonds, are much weaker, and their boiling points lower. These attractive forces cause ethers to dissolve in water to approximately the same extent as comparably constituted alcohols. Alkanes cannot engage in hydrogen bonding to water.

39. The methods of extraction of ethers: From alkoxides: CH3CH2ONa + CH3I → CH3CH2OCH3 + NaI 2. Dehydration of alcohols (dehydration between 2 molecules):

41. Chemical properties of ethers Reaction with concentrated mineral acids (formation of oxonium salts): A second dangerous property of ethers is the ease with which they undergo oxidation in air to form explosive peroxides. Air oxidation of diethyl ether proceeds according to the equation

42. The reaction follows a free-radical mechanism and gives a hydroperoxide, a compound of the type ROOH. Hydroperoxides tend to be unstable and shock-sensitive. On standing, they form related peroxidic derivatives, which are also prone to violent decomposition. Air oxidation leads to peroxides within a few days if ethers are even briefly exposed to atmospheric oxygen. For this reason, one should never use old bottles of dialkyl ethers, and extreme care must be exercised in their disposal. 3. Reaction with HI CH3−O−CH3 + HI → CH3−OH + CH3I

43. The mechanism for the cleavage of ethers by hydrogen halides, using the reaction of diethyl ether with hydrogen bromide as an example. Step 1: Proton transfer to the oxygen of the ether to give a dialkyloxonium ion.

44. Step 2: Nucleophilic attack of the halide anion on carbon of the dialkyloxonium ion. This step gives one molecule of an alkyl halide and one molecule of an alcohol. Step 3 and Step 4: These two steps do not involve an ether at all. They correspond to those in which an alcohol is converted to an alkyl halide .

45. 11. Enols Enols (also known as alkenols) are alkenes with a hydroxyl group affixed to one of the carbon atoms composing the double bond. Enols and carbonyl compounds (such as ketones and aldehydes) are in fact isomers; this is called keto-enol tautomerism: The enol form is shown above on the left. It is usually unstable, does not survive long, and changes into the keto (ketone) form shown on the right. This is because oxygen is more electronegative than carbon and thus forms stronger multiple bonds. Hence, a carbon-oxygen (carbonyl) double bond is more than twice as strong as a carbon-oxygen single bond, but a carbon-carbon double bond is weaker than two carbon-carbon single bonds.

46. The name of enols systematic nomenclature IUPAC form the name alkene to which is added the suffix-ol: CH2=CH-OH CH2=CH-CH2-OH ethenol, vinyl alcohol Propenol-1(unsaturated alcohol) Hydration of acetylene as the intermediate substance is formed vinyl alcohol (enol), which isomerization in acetic aldehyde. H2O,Hg²+,H+ C2H2 CH2=CH-OH This property of enols characterizes the rule of Eltekov-Erlenmeyer. - Compounds in which the hydroxyl group located at carbon atoms that forms a fold communication, unstable and isomerizationof carbonyl compounds - aldehydes and ketones

47. Aminoalcohols Amino alcohols are organic compounds that contain both an amine functional group and an alcohol functional group. NH2-CH2-CH2-OH N(C2H5)-CH2-CH2-OH 2-aminoethanol 2-N,N- diethylaminoethanol Ifthemoleculeof aminoalcoholcontainstheinitscompositiontwoorthreehydroxyalkylnesgroups, throughthe combinationofnitrogenatom, inthiscase, thebasistakesthenameamine. OH-CH2-CH2-NH-CH2-CH2-OH di (β-oxyethyl) amine, or di (2-hydroxyethyl) amine

48. The methods of extraction of aminoalcohols Accessionofammoniaoraminestotheα-oxyses. CH2-CH2 + NH3 NH2-CH2-CH2-OH O 2. Reduction of nithroarenes. CH3-CH(NO2)-CH2-OH + 3H2 CH3-CH(NH3)-CH2-OH + 2H2O Chemical properties of aminoalcohols Aminoalcoholsshowpropertiesasalcoholsandamines. As a basisaminoalcoholsformsaltswithmineralacids. OH-CH2-CH2-NH2 + HCl OH-CH2-CH2-NH3Cl¯

49. The nomenclature and isomery of mononuclear phenols Numbering of the ring begins at the hydroxyl-substituted carbon and proceeds in the direction that gives the lower number to the next substituted carbon. Substituents are cited in alphabetical order.

50. C C N C H N C H C H O H O 3 3 2 5 H H O O Phenacetin (p-еthoxyacethanilide) Paracetamol,(N-acetyl-p-aminophenol p-hydroxyacethanilide), N H C H O 2 2 5 Phenetidine (p-ethoxyaniline)