Alcohols, Thiols , Phenols, And Ethers

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ALCOHOLS, THIOLS, PHENOLS, AND ETHERS IUG, Fall 2013 Dr. Tarek Zaida 1

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IUG, Fall 2013 Dr. Tarek Zaida. 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 Alcohols are derivatives of hydrocarbons in which 1 or more of the hydrogen atoms has been replaced by a hydroxyl (-OH) functional group. - PowerPoint PPT Presentation

Transcript of Alcohols, Thiols , Phenols, And Ethers

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ALCOHOLS, THIOLS, PHENOLS, AND ETHERS IUG, Fall 2013

Dr. Tarek Zaida

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1. ALCOHOLS 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hydrocarbons in which 1 or more of the hydrogen atoms has been replaced by a hydroxyl (-OH) functional group.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.

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GENERAL STRUCTURAL FORMULAS OF ALCOHOLS, THIOLS, PHENOLS, AND ETHERS

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NAMING ALCOHOLS 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.

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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.,

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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:

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USES OF ALCOHOLS

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.

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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.

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PREPARATION1. By distillation of wood2. It is prepared commercially from

carbon monoxide:

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2. ETHANOL (ETHYL ALCOHOL) 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?

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ANSWER 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.

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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.

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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.

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PREPARATION OF ETHANOL1. From Sucrose (cane sugar)

2. Synthetically can be prepared from ethene:

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3. 2-PROPANOL (ISOPROPYL ALCOHOL) 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.

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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.

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- 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.

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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

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MEDICAL USE OF NITROGLYCERIN 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 guanylate

cyclase, which in turn catalyzes the synthesis of cGMP which acts as a signal that induces muscular relaxation in the blood vessel.

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OTHER ALCOHOLS 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

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2. Cholesterol: A very important steroid in the human body

3. Retinol (Vitamin A): important in vision

Tocopherol (Vitamin E): a very strong antioxidant

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TYPES OF ALCOHOLS

1. Primary alcohols 2. Secondary alcohols 3. Tertiary alcohols

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REACTIONS 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.

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

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2. Formation of Ethers

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3. Oxidation: Primary alcohols can be oxidized to

form aldehyde, Further oxidation of aldehyde yields an

acid.

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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

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

esters.

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2. THIOLS Are sulfur analogs of alcohols and

contain an -SH functional group in place of an –OH group

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NAMING THIOLS ACCORDING TO IUPAC Just add the ending thiols 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.

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Thiols are sometimes called mercaptans, a name that refers to their reaction with

mercuric ion to form mercury salts, called mercaptides.

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PROPERTIES OF THIOLS 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.

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PREPARATION 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-Rdisulfide

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3. PHENOLS When –OH is attached to benzene ring,

phenol is formed.

Unlike alcohols, phenols are weak acids

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Phenols react with aqueous solution of sodium hydroxide to form a soluble salt:

Uses of Phenols:1. As antiseptic2. As disinfectant

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4. ETHERS 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

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NAMING ETHERS Ethers are usually named by giving the

name of each alkyl or aryl group, in alphabetical order, followed by the word ether.

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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.

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PROPERTIES OF ETHERS 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.

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ETHER AS ANESTHETIC Used as a general anestheticAdvantages:1. Easy to administer2. Excellent muscular relaxant3. Little effect on respiration, blood

pressure

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Disadventage:1. Very flammable2. Irritating to membrane of respiratory tract

Today ether as anesthetic has been replaced by:

Halothane Nitrous oxide Enflurane