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![O O
H2SO4
H3C—CH2—OH + H3C—C—OH H3C—CH2—O—C—CH3 + H2O
Ethanol Acetic Acid Ethyl Acetate
Other Reactions of Alcohols:
1: Oxidation:
Oxidation of Alcohols forms aldehydes and ketones.
Primary alcohols give aldehydes, while secondary alcohols give ketones.
Best reagent for this purpose is Acid Dichromate.
H3C—CH2—OH + [O] + H3C—C — H + H2O
Ethanol Acetaldehyde
H3C H3C
CH—OH + [O] C
O
H3C
H3C
K2Cr2O7
K2Cr2O7
H2SO4
H2SO4
2-Propanol Acetone
3: Reaction with Acetic Acid:](https://image.slidesharecdn.com/alcohol-260104182830-3e119dc8/85/ALCOHOL-pptxndndndndmdmdmdmdmmdmdmdmdmdmdmdmddmmddm-13-320.jpg)
ALCOHOL.pptxndndndndmdmdmdmdmmdmdmdmdmdmdmdmddmmddm
- 1. ALCOHOL BY: USMAN ALI ALIZARYAB AHAD ISLAM HANZALA AHMED
- 2. ALCOHOL Compounds inwhich a Hydroxyl group is attached to an alkyl group are called Alcohols. Their general formula is “ R-OH “ For Example: H3C--CH2—OH : H3C--CH2—CH2—OH Ethanol Propanol TYPES: On the basis of number of hydroxyl groups, alcohols may be classified into 2 types. Monohydric Alcohols. Polyhydric Alcohols.
- 3. MONOHYDRIC ALCOHOLS: These contain only one –OH Group in their molecule. For Example : H3C—OH H3C—CH2—OH Methanol Ethanol POLYHYDRIC ALCOHOLS: These contain two or more –OH groups in their molecule. For Example: H2C—CH2 H2C—CH—CH2 │ │ │ │ │ OH OH OH OH OH Ethylene Glycol Glycerol
- 4. CLASSIFICATION OFMONOHYDRIC ALCOHOLS: Monohydric Alcohols can be further classified into 3 types: 1: Primary Alcohols: In these, the Carbon attached to the –OH group is further attached with only one Carbon atom. H3C--CH2—OH H3C--CH2—CH2—OH Ethanol Propanol 2: Secondary Alcohols: In these, the carbon attached to the –OH group is further attached to two more carbon atoms. H3C--CH—OH H3C--CH2—CH—OH │ │ CH3 CH3 2-Propanol 2-Butanol
- 5. 3: Tertiaryalcohols: In these, carbon attached to the –OH group is further attached to three more carbon atoms. CH3 │ H3C—C—OH │ CH3 2-Methyl-2-propanol METHODS OF PREPARATION OF ALCOHOLS: There are several methods for the preparation of Alcohols. INDUSTRIAL PREPARATIONS: 1: From water gas: Methyl alcohol is obtained by passing water gas over heated zinc oxide and chromium oxide at 450-500 C under 200 Atmospheric Pressure.
- 6. CO +2 H2 H3C—OH Methanol From Molasses: The residue obtained after the crystallization of sugar from concentrated sugar cane juice is called molasses. ZnO / Cr2O3 450-500° C 200atm
- 7. It isfermented by enzymes present in yeast to give ethanol. C12H22O11 + H2O C6H12O6 + C6H12O6 Molasses Glucose Fructose C6H12O6 2 C2H5OH + CO2 Ethanol From STARCH: Ethanol can also be prepared from starch by the action of multiple enzymes. 2 (C12H22O11) + nH2O n(C12H22O11) Starch Maltose C12H22O11 + H2O 2 C6H12O6 Glucose Invertase Zymase yeast yeast yeast yeast diastase Maltase
- 8. C6H12O6 2 C2H5OH+ CO2 Ethanol OTHER METHODS FOR PREPARATION OF ALCOHOL: Hydrolysis of Alkyl Halides: R—Br + NaOH R—OH + NaBr H3B—CH2—Br + NaOH H3C—CH2—OH + NaBr From Alkenes: Alkenes dissolve in Sulfuric Acid to form alkyl hydrogen sulphates. H2C CH2 + H2SO4 H3C--CH2—OSO3H Ethylene Sulfuric Acid Ethyl Hydrogen Sulfate Zymase yeast Heat Heat
- 9. Alkyl HydrogenSulphate on boiling with water gives alcohols. H3C--CH2—OSO3H + H2O H3C--CH2—OH + H2SO4 Reduction of Aldehydes and Ketones: Aldehydes on reduction with Ni or Pt or Pd and H2 or with NaBH4 give alcohols. Aldehydes give primary alcohols while ketones give secondary alcohols. 100 °C
- 10. Chemical propertiesand Reactions of Alcohols: Alcohol reacts with other reagents in two ways: 1: Reactions in which C—O bond breaks. 2: Reactions in which O—H bonds breaks. If a nucleophile attacks then C—O bond breaks. H3C—CH2—OH H3C—CH2 + + HO- If an electrophile attacks then O—H bond breaks. H3C—CH2—O—H H3C—CH2 –O- + H+ nucleophile electrophile E.G. HCL E.G. Na
- 11. Reactions inwhich C—O bond breaks: 1: Reaction with Thionyl Chloride: H3C—CH2—OH + SOCL2 H3C—CH2—CL + SO2 + HCL Thionyl Chloride ChloroEthane 2: Reaction with Hydrochloric Acid: H3C—CH2—OH + HCL H3C—CH2—CL + H2O ChloroEthane 3: Reaction with Ammonia: H3C—CH2—OH + H—NH2 H3C—CH2—NH2 + H2O Ethaneamine pyridine ZnCL2 ThO2
- 12. Reactions inwhich O—H bond breaks: 1: Reaction with Sodium: 2 C2H5O--H + 2Na 2 C2H5O—Na + H2 Sodium Ethoxide 2: Reaction with Grignard’s Reagent: Br H3C—Mg—Br + H3C—CH2—OH CH4 + Mg Methyl Magnesium Bromide Methane Magnesium ethoxy bromide OCH2CH3 Ether
- 13. O O H2SO4 H3C—CH2—OH + H3C—C—OH H3C—CH2—O—C—CH3 + H2O Ethanol Acetic Acid Ethyl Acetate Other Reactions of Alcohols: 1: Oxidation: Oxidation of Alcohols forms aldehydes and ketones. Primary alcohols give aldehydes, while secondary alcohols give ketones. Best reagent for this purpose is Acid Dichromate. H3C—CH2—OH + [O] + H3C—C — H + H2O Ethanol Acetaldehyde H3C H3C CH—OH + [O] C O H3C H3C K2Cr2O7 K2Cr2O7 H2SO4 H2SO4 2-Propanol Acetone 3: Reaction with Acetic Acid:
- 14. 2: Dehydration: Alcohols react with concentrated Sulfuric Acid to give different products at different temperatures. High Temperature and Low Alcohol Concentration. H2C—CH2 H2C CH2 + H2O Ethene H OH Ethanol Low Temperature and High Alcohol Concentration. H3C—CH2—OH H3C—CH2 + O + H2O H3C—CH2—OH H3C—CH2 Ethanol Diethyl ether H2SO4 180 °C 140 °C H2SO4
- 15. 3: Reactionwith phosphorus pentahalide: H3C—CH2—OH + PCL5 H3C—CH2—CL + POCl3 + HCl Uses Of Alcohols: Alcohols are used as: Solvents (oils, paints and varnishes) Antifreeze agents in radiators. Fuel In some countries. Preservatives for biological specimen. Drinks. PHARMACEUTICAL USES: Some pharmaceutical uses of Alcohols are :
- 16. Wound Dresser:Alcohol is used as an anti-septic as it has bactericidal effects. E.g: Alcohol in Dettol. Cough and Cold: Alcohol is found in most cough syrups as it has soothing effect on throat and it also helps in curing cold and nose congestion. Hand Disinfectant: It is the most common pharmaceutical use of Alcohol. It has anti- fungal and anti-bacterial effects and thus, is used in most hand sanitizers. In Filtration: Alcohol is also used in processes like filtration, distillation and removal of impurities from a drug. As Solvent: Alcohol is an excellent solvent for many drugs. Temazepam: It is used in the treatment of insomnia and contains isopropyl and iso butyl alcohol. E.g. Brand name: Restoril.
- 17. Amoxicillin Trihydrate:Amoxicillin is used to treat bacterial infections and dental abscess. It contains alcohols, Iso-Propanol as active agents. Brand Name: Amoxin And Larotid. Bupropion Hydrochloride: It acts as anti-depressant and used in the treatment of depressive disorder. Brand Name: Wellbutrin. Dental Gel: Corsodyl dental gel is used to treat gum diseases, recurring mouth ulcers, prevent cavities and maintain mouth hygiene. It is made of 7.5% alcohol. Codimol DM: (Dm = Dextromethophan) It is used to treat symptoms caused by common cold , flu, allergies or other breathing illnesses. It has Iso-propyl Alcohol and Iso-Butyl Alcohol. E.g. : Brand name = Promethazine DM Zonisamide: Zonisamide is an inhibitor that contains isopropyl alcohol and butyl alcohol and is used in the treatment of seizure. Brand name: Zonegran. Used as diluent: Alcohols act as diluent for many drugs, especially in homeopathy treatment. A small amount of a drug can be diluted in alcohol , which is totally harmless to the body.
- 18. PHYSICAL PROPERTIES: Lower alcohols are generally colorless liquids. (Methanol , Ethanol) They have a characteristic sweet smell and burning taste. Lower alcohols are readily soluble in water but solubility decreases in higher alcohols. The solubility of alcohols is due to hydrogen bonding which is present in lower alcohols but less in higher alcohols. H+ —O+ - - - - H- —O+ │ │ R H Melting and boiling points of alcohols are higher than corresponding alkanes E.g. Methyl alcohol and Ethyl Alcohols are liquids while methane and ethane are gases. This is also due to hydrogen bonding in alcohols.
- 19. Identification Testsfor Alcohols: 1: Oxidation test (Dichromate test): In this test, the alcohols are treated with sodium dichromate(Na2Cr2O7) In sulfuric acid (Orange Solution). The rate of oxidation varies between primary, secondary and tertiary alcohols . On the basis of their oxidation rates, alcohols can be distinguished as: Primary alcohol gets easily oxidized to an aldehyde and further be oxidized to carboxylic acid. There will be a change in color of solution from orange to green. Secondary Alcohol gets oxidized to ketone but further oxidation is not possible . There will be a change in color of solution from orange to green. Tertiary alcohol doesn’t get oxidized. Solution remains orange.
- 20. orange to green. orangeto green. Solution remains orange.
- 21. 2:Ceric ammoniumnitrate test: Alcohol reacts with ceric ammonium nitrate (Yellow Colour) to form alkoxy cerium compound (Pink or Red Colour) 2R—OH + (NH4)2Ce(NO3)6 (ROH)2Ce(NO3)4 + 2NH4NO3 Alcohol Ceric ammonium nitrate Alkoxy cerium compound Ammonium Nitrate Yellow Color Pink or Red Color 3:Sodium Metal Test: When pure (Dried) Sodium metal is added to a solution containing alcohol, it creates bubbles in the solution due to evolution of hydrogen gas. This evolution of hydrogen gas indicates the presence of an alcohol. This reaction is a vigorous reaction as Sodium metal reacts explosively. R—OH + Na RO- Na+ + H2
- 22. 4: LucasTest: Primary, Secondary and Tertiary alcohols are identified by reacting them with conc. HCL in Anhydrous Zinc Chloride . An oily layer of alkyl halides is formed in these reactions. Tertiary Alcohols form an oily layer immediately. Secondary Alcohols form an oily layer in five to ten minutes. Primary Alcohols form an oily layer only on heating. Primary: R—CH2—OH + HCL R—CH2—Cl + H2O CH3CH2OH + HCL CH3CH2Cl + H2O Secondary: R R CH—OH + HCl CH—CL + H2O R R ZnCl2 ZnCl2 ZnCl2 Ethanol Ethyl Chloride Oily Layer on Heating
- 23. CH3 CH3 CH—OH + HCl CH—Cl + H2O CH3 CH3 R C OH + HCL C Cl + H2O C OH + HCL C Cl + H2O ZnCl2 ZnCl2 R R R R R ZnCl2 CH3 CH3 CH3 CH3 CH3 CH3 Tertiary: Sec-Butyl Alcohol Sec-Butyl Chloride Tert-Butyl Alcohol Tert-Butyl Chloride Oily Layer after 5-10 minutes Oily Layer formed immediately
- 24.