Alcohols, Phenols and Thiols, and ethers

Nomencalture of alcohols Use the end ol Examples

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.

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.

Acidity of Alcohols Acids are proton donors.

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)

Types of alcohols Methyl alcohol Isopropyl alcohol tert- butyl alcohol 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 (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)

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)

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.

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)

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.

Ethylene glycol IUPAC (International Union for Pure and Applied Chemistry) name: 1,2 ethanediol Ethylene glycol is a dihydric alcohol: It has a high boiling point 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.

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.

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.

Reactions of alcohols Dehydration: Ethene Ethanol

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

Thiols Methanethiol 2-propanethiol methylmercaptan isopropylmercaptan 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.

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:

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.

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

Phenols o-Cresol m-Cresol p-Cresol 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. o-Cresol m-Cresol p-Cresol

Phenols BHA BHT Hexyl resorcinol 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

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.

Methoxy propane Methyl propyl ether Diethyl ether Ethyl ether 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

Isoflurane Enflurane 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