Alcohols, Thiols , Phenols, And Ethers

IUG, Fall 2013 Dr. TarekZaida Alcohols, Thiols, Phenols, And Ethers

Alcohols are derivatives of hydrocarbons in which 1 or more of the hydrogen atoms has been replaced by a hydroxyl (-OH) functional group. Functional group: a particular arrangement of a few atoms that imparts certain characteristic properties to an organic molecule. 1. Alcohols

General structural formulas of alcohols, thiols, phenols, and ethers

In the IUPAC system, the hydroxyl group in alcohols is indicated by the ending -ol. In common names, the separate word alcohol is placed after the name of the alkyl group. The following examples illustrate the use of IUPAC rules, with common names given in parentheses. Naming alcohols

The general formula of alcohols is R-OH Where R indicates the Alkyl group attached to an –OH R could be: CH3, CH3CH2- CH3CH2CH2-, ect.,

Alcohols are soluble in H2O because of the –OH group. • But as the length of the carbon chain increases, the solubility decreases • Alcohols react with acids to give compounds called esters:

1. Methyl alcohol (methanol) CH3OH Commonly Known as wood alcohol The U.S. production of methanol is 1.4 billion gallons per year. Most of it is used to produce formaldehyde and other chemicals, Is also used as an anti-freeze. Used as a solvent in many industrial reactions. USES OF ALCOHOLS

It should never be applied to the body neither should the vapors be inhaled because it can be absorbed both through the skin and through the respiratory tract. Ingestion as little as 15 ml can cause blindness (it is oxidized to formaldehyde (CH2=O), which binds to opsin, preventing formation of rhodopsin, the light-sensitive pigment needed for vision. While 30 ml are enough to cause death.

By distillation of wood It is prepared commercially from carbon monoxide: Preparation

Known as grain alcohol It has an important property: it denatures proteins (that’s why it is used as antiseptic in hospitals). As antiseptic, 70% alcohol is preferred to a stronger solution 100%, why? 2. Ethanol (ethyl alcohol)

Ethanol causes protein to coagulate on contact, a 100% solution coming into contact with a microorganism creates a hardened protein wall around the outside of the organism, rather than permeating into its interior. Because microorganisms can be very resilient, this protein shell only causes dormancy rather than death. Answer

This can lead to revival and a continuation of the cycle of reproduction under the right circumstances. At a purity of 70%, however, the alcohol causes coagulation to occur more gradually, slowing down the microorganism from the inside out.

Ethanol is also used as a sponge bath because it evaporates rapidly (bp: 78 C) by the heat of the patient’s skin. However Water is used instead of ethanol for sponge bath because it is cheaper. Ethanol is also used as a solvent for many substances.

From Sucrose (cane sugar) Synthetically can be prepared from ethene: Preparation of Ethanol

Is toxic Used as a stringent. Used as a rubbing alcohol (can be applied as a cooling, soothing application for bedridden patients and athletes. It is also widely used for cleansing surgeons' hands and instruments and for the disinfection of skin prior to penetration by a hypodermic needle. Is manufactured commercially by the acid-catalyzed hydration of propene. 3. 2-Propanol (isopropyl alcohol)

4. Ethylene glycol (1,2-ethanediol) • Ethylene glycol is used: • as antifreeze in cooling and heating systems, • in hydraulic brake fluids, • as a solvent in the paint and plastics industries, in the formulations of printers' inks. • As additive in moisturizer of the skin.

Ethylene glycol is toxic because it is oxidized in the lever to oxalic acid, which crystalizes as calcium oxalate in kidney, causing renal damage, which can lead to kidney failure. • Antidote for ethylene glycol & methyl alcohol is the administration of high level of ethanol. • Ethanol will force liver enzymes to oxidize ethanol instead of poisonous alcohol which is presented in smaller amounts.

5. Glycerol (glycerin) • An example of a trihydric alcohol. • Glycerol is important in terms of body chemistry; it is a constituent of fats. • It is a by-product in soap manufacture. • It is used in preparation of cosmetics & hand lotions, suppositories. • Is used in labs as a lubricant for rubber tubing & stoppers. • When treated with nitric acid it forms nitroglycerin. 1,2,3-propanetriol

Is used to treat angina or heart pain It causes a dilation of coronary arteries, Thus increasing the supply of blood to heart muscle. How does nitroglycerin work? Liberates nitric oxide from endothelial cells of blood vessels. NO binds to heme component of enzyme guanylatecyclase, which in turn catalyzes the synthesis of cGMP which acts as a signal that induces muscular relaxation in the blood vessel. Medical use of nitroglycerin

1. Menthol: a cyclic alcohol It is used in cosmetics and shaving lotions, due to it’s cooling and refreshing feeling when rubbed on the skin. It is also used in cough drops & nasal sprays OTHER ALCOHOLS

2. Cholesterol: A very important steroid in the human body 3. Retinol (Vitamin A):important in vision Tocopherol (Vitamin E):a very strong antioxidant

1. Primary alcohols 2. Secondary alcohols 3. Tertiary alcohols Types of Alcohols

1. Dehydration of alcohols: Alcohols can be dehydrated by heating them with a strong acid. For example, When ethanol is heated at 180°C with a small amount of concentrated sulfuric acid, a good yield of ethylene is obtained. Reactions of Alcohols

Write the dehydration reaction of 2 CH3-CH2-CH2-CH(OH)-CH3?

2. Formation of Ethers

3. Oxidation: Primary alcohols can be oxidized to form aldehyde, Further oxidation of aldehyde yields an acid.

Secondary Alcohols can be oxidized to give ketones Tertiary alcohols, having no hydrogen atom on the hydroxyl-bearing carbon, do not undergo this type of oxidation

4. Forming esters: Alcohols react with organic acids to give esters.

Are sulfur analogs of alcohols and contain an -SH functional group in place of an –OH group 2. Thiols

Just add the endingthiols to the name of the parent hydrocarbon. Note: The e is not deleted from the parent alkane. Common name of thiols were formed by first naming the alkyl group and then adding the word mercaptan. Naming Thiols according To IUPAC

Thiols are sometimes called mercaptans, a name that refers to their reaction with mercuric ion to form mercury salts, called mercaptides.

Many thiols are found in nature. They have unpleasant odor. Onion when cut, releases 1-propanethiol HS-CH2-CH2-CH3 The odor of garlic is due to thiols. Skunk when attacked it releases thiols. Thiols added to heating - & cooking- gas to detect gas leak. Properties of thiols

By heating alkyl halides with NaHS (sodium hydrogen sulfide). CH3-CH2-CH2-Cl + NaHS CH3-CH2-CH2-SH + NaCl Thiols are easily oxidized to disulfides: 2 R-CH2-SH O2 R-CH2-S-S-CH2-R Preparation of thiols disulfide

When –OH is attached to benzene ring, phenol is formed. Unlike alcohols, phenols are weak acids 3. Phenols

Phenols react with aqueous solution of sodium hydroxide to form a soluble salt: Uses of Phenols: 1. As antiseptic 2. As disinfectant

All ethers are compounds in which two organic groups are connected to a single oxygen atom. The general formula for an ether is R-O-R’ where R and R’ may be identical or different, and they may be alkyl or aryl groups. In the common anesthetic, both R and R’ are ethyl groups. CH3CH2-O-CH2CH3 4. ethers

Ethers are usually named by giving the name of each alkyl or aryl group, in alphabetical order, followed by the word ether. Naming ethers

For ethers with more complex structures, it may be necessary to name the -OR group as an alkoxy group. In the IUPAC system, the smaller alkoxy group is named as a substituent.

Low boiling point They are good solvents because they do not react with solutions. Ethyl ether is used to extract organic materials from naturally occurring substances. Properties of ethers

Used as a general anesthetic Advantages: Easy to administer Excellent muscular relaxant Little effect on respiration, blood pressure Ether as anesthetic

Disadventage: Very flammable Irritating to membrane of respiratory tract Today ether as anesthetic has been replaced by: Halothane Nitrous oxide Enflurane

Alcohols, Thiols , Phenols, And Ethers