Alcohols, Phenols and Thiols , and ethers

1. Alcohols, Phenols and Thiols, and ethers

2. Nomencalture of alcohols Use the end ol Examples

4. Hydrogen bonding in alcohols and phenols • Alcohols and phenols form hydrogen bonds, and hence they have relatively high boiling points. This also makes the lower alcohols miscible with water. As the R group becomes larger, the solubility of alcohols in water decreases dramatically.

5. Hydrogen bonding • Hydrogen bonding occurs between molecules where you have a hydrogen atom attached to one of the very electronegative elements - fluorine, oxygen or nitrogen.

6. Acidity of Alcohols Acids are proton donors.

7. The acidity increases as the negative charge at the OH decreases (delocalized): • phenols are more acidic than Alcohols due to resonance effect (delocalization of the negative charge)

8. Types of alcohols • Primary alcohols (1°): contains an OH- functional group that has one or no carbon atoms attached to it; Example: Methyl alcohol • Secondary Alcohols (2°): contains an OH- functional group that has two carbon atoms attached to it; Example: Isopropyl acohol. • Tertiary Alcohols (3°): contains an OH- functional group that has three carbon atoms attached to it. Methyl alcohol Isopropyl alcohol tert- butyl alcohol

9. Methyl Alcohol (Methanol) • Known as wood alcohol due to preparation from the distillation of wood. • Commercially prepared from CO according to: • CO + 2H2 CH3OH (Pt catalyst, heat) • CH3OH is an important solvent. • CH3OH is toxic. (ingestion of 15 ml  blindness, 30 ml  death). • Should never be inhaled nor applied to the skin. (good absorption from both tissues)

10. Ethyl Alcohol (Ethanol) • In hospital the word alcohol means ethyl alcohol. • Can be prepared from the fermentation blackstrap molasses (residues resulting from the purification of can sugar) under the influence of yeast enzymes. C12H22O11 + H2O  4 C2H5OH + CO2 • Grain alcohol  grain starch  sugar by malt  fermentation. • Synthetic preparation from ethene (Catalyst: Silicon dioxide)

11. Ethyl Alcohol (Ethanol) • The property of ethanol as an antiseptic agent is based on its ability to denaturate proteins. • Cave: the antiseptic property of 70% ethanol solution (in water) is better than 100 % ethanol. • Explanation: 100 % ethanol leads to the coagulation (تخثر) of proteins in the cell wall of bacteria (or other one-cell organisms), which builds a ring preventing further ethanol to enter the inside of the bacteria and to coagulate other proteins there. 70% ethanol, however, coagulates proteins to a slower rate allowing ethanol to penetrate (نفذ الى) the cell inside of bacteria and coagulate proteins there.

12. Ethyl Alcohol (Ethanol) • Ethanol ( better than water) can be used for sponge baths to reduce fever (حرارة) from patients. When placed on skin  rapid removal. Evaporation needs heat, which comes from patient’s skin lowering temperature. (cave: ethanol is flammable(قابلة للاشتعال)) • Ethanol is a solvent for many substances. A solutions are called tinctures (Example: iodine tincture). • Alcohol is used as a beverage depression of nervous system, removal of individual’s inhibition. Excessive use  cirrhosis (liver destruction)

13. Isopropyl alcohol • According to IUPAC isopropyl alcohol is called 2-propanol. • Is toxic, and therefore should not be taken internally. • It does not get into the skin. Therefore, it can be used as rubbing alcohol.

14. Ethylene glycol • IUPAC (International Union for Pure and Applied Chemistry) name: 1,2 ethanediol • Ethylene glycol is a dihydric alcohol: • It has a high boilingpoint due to extensive hydrogen bonding. • It is completely miscible with water. • It is extremely toxic if taken internally (Metabolism to oxalic acid  Crystallization as calcium oxalate  kidney stones). • Antidote: administration of high levels of ethanol Why? High levels cause the liver to metabolize the ethyl alcohol rather than the toxic alcohol. • Uses: Skin moistures, anti freeze in cars.

15. Glycerol • IUPAC name: glycol 1,2,3 propanetriol • Glycerol is a trihydric alcohol • Important constituent of body lipids. • Byproduct by the manufacture of soap. • Uses: preparation of cosmetics, hand lotions, suppositories, in rubber tubing and stoppers, preparation of nitroglycerin. • Nitroglycerin (Glycerin + Nitric acid) is an explosive but also an important medication for the treatment of heart pain by dilatation of coronary arteries better supply of blood of heart muscle.

16. Other alcohols:Menthol • Menthol is a cyclic compound. • It has a cooling refreshing effect, when rubbed on the skin. • It is used in cosmetics, shaving lotions, cough drops, and nasal sprays.

17. Reactions of alcohols • Dehydration: Ethene Ethanol

18. Reactions of alcohols 2. Formation of ethers: using H2SO4. The conditions are, however, different from those used for the formation of alkenes. 3. Oxidation:Alcohol  Aldehyde  Carboxylic acid  CO2 + H2O. Note: • Secondery alcohols  Ketones • Tertiary alcohols  (under ordinary conditions) 4. Formation of esters: Alcohol + carboxylic acid Ester + H2O

19. Thiols Methanethiol 2-propanethiol • Thiols are sulfur analogs to alcohols but contain –SH functional group in place of an –OH group. • Nomenclature: -Add the adding thiol to the name of the parent hydrocarbon -The e-ending of the parent hydrocarbon is not deleted. -Common Names: Alkyl group + the word mercaptan. methylmercaptan isopropylmercaptan

20. Thiols • Thiols have a disagreeable odor (Onion[1-propanethiol, garlic, added to natural gas to enable better detection). • They do not exhibit hydrogen bonding  lower boiling point than the corresponding alcohols. • They are less soluble in water than corresponding alcohols. • Thiols are important in enzymes involved in carbohydrate metabolism. • Preparation: heating of alkyl halide * Sodium hydrogen sulfide:

21. Thiols • Thiols are easily oxidized to disulfides • Example for such an oxidation from the biochemistry: • Disulfide bonds are involved in the formation of the tertiary structures of proteins.

22. Phenols • Benzene with OH group  Phenols. • Phenols are generally like alcohols but they are weak acids and alcohols are not. • Phenol + NaOH  Sodium phenoxide + H2O • Phenol is posinous if taken internally, and externally it causes deep burns on the skin. • Antidote on the skin: 50 % alcohol, glycerin, sodium bicarbonate solution, water. • Phenol is a disifictant for surgical instruments, clothing, toilts and sinks. • Phenol is used in the manufacture of dyes (الأصباغ)and plastics

23. Phenols • Phenol is a standard reference for germicidal (مبيد للجراثيم) activity disinfectants(مطهر). • Phenol coffecient 5 = 1% desinfectant = 5% Phenol solution. • Cresol (mixture) is a better antiseptic(مطهر) than phenol but should be used only externally. m-Cresol o-Cresol p-Cresol

24. Phenols Hexyl resorcinol is a better antiseptic and germicide than resorcinol and is used in mouth washes. Butylated hydroxy anisol (BHA)and butylated hydroxy toluene (BHT) are used as food preservative (cave: allargy). BHA BHT Hexyl resorcinol

25. Ethers • Properities of ethers • No hydrogen bonds  low boiling points  easily moved and recovered • Inert (do not react with other substances)  good solvents  Extraction of organic material. • Very flammable (care must be taken) • Formation of peroxides if left in the lab for long time (extermely explosive)  not allowed to stand exposed to air for long period of time.

26. Nomenclature • IUPAC: If different alcohols are reacted a mixed ether is formed; Mixed ethers are named as alkoxy derivatives (المشتقات) of hydrocarbons with the shorter chain named as the alkoxy group and the longer chane as the alkane. • Common system: Mixed ethers are named by listing the alkyl groups followed by the word ether. Methoxy propane Methyl propyl ether Diethyl ether Ethyl ether

27. Uses • Ethylether has been used as anesthetic (مخدر) for long time (muscle relaxant (ارتخاء العضلات), little effect on respiration rate, blood pressure, pulse rate). However: flammable, irritant to the membranes of the respiratory tract, nausea (غثيان). •  Replaced by non flammable enflurane and isoflurane Isoflurane Enflurane