Alcohols, Phenols and Thiols , and ethers

27
Alcohols, Phenols and Thiols, and ethers

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Alcohols, Phenols and Thiols , and ethers. Nomencalture of alcohols Use the end ol Examples. Hydrogen bonding in alcohols and phenols. - PowerPoint PPT Presentation

Transcript of Alcohols, Phenols and Thiols , and ethers

Page 1: Alcohols, Phenols and  Thiols ,  and ethers

Alcohols, Phenols and Thiols, and ethers

Page 2: Alcohols, Phenols and  Thiols ,  and ethers

Nomencalture of alcoholsUse the end olExamples

CH3OH CH3CH2CH2OHCH3CH2OHCH3CHCH3

OH

CH3

CH2OHCH3

CH3 C OH

CH3

CH3

Methanol Ethanol 1-propanol 2-propanolMethyl alcohol ethyl alcohol propyl alcohol isopropyl alcohol

CH2 = CH - CH2OH

2-methyl-1-propanol 2-methyl-2-propanol 2-propen-1-ol isobutyl alcohol tert-butyl alcohol allyl alcohol

Page 3: Alcohols, Phenols and  Thiols ,  and ethers

OHOH

OHOH

C CCH3 CH2

CH2OH

OH

OH

NO2

OH

COOH

OH

CHO

cyclopentanol cis-1,2-cyclopentandiol 2-phenylethanol

3-pentyn-1-ol phenol p-nitrophenol

o-hydroxybenzoic acid salicylic acid

m-hydroxybenzaldehyde

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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.

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• 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.

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Acidity of AlcoholsAcids are proton donors.

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The acidity increases as the negative charge at the OH decreases (delocalized):

a) phenols are more acidic than Alcohols due to resonance effect (delocalization of the negative charge)

Page 8: Alcohols, Phenols and  Thiols ,  and ethers

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.

CH

HOHH

Methyl alcohol

C

H

OH

CH3CH3

Isopropyl alcohol tert- butyl alcohol

C

CH3

OH

CH3CH3

Page 9: Alcohols, Phenols and  Thiols ,  and ethers

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)

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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(

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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 ( الى the cell inside of (نفذbacteria and coagulate proteins there.

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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( لالشتعال ((قابلة

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)

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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.

CH3CH3

OH

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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.

OH OH

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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.

OH OH

OH

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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.

OH

CH3

CH3

CH3

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Reactions of alcohols1. Dehydration:

CH3 OHH2SO4

180°C

OH

H2SO4 180°C

+

2-pentanol 2-penten 1-penten

Ethanol Ethene

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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: a. Secondery alcohols Ketonesb. Tertiary alcohols (under ordinary

conditions)4. Formation of esters: Alcohol +

carboxylic acid Ester + H2O

Reactions of alcohols

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Thiols

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.

CH3 SHMethanethiol

methylmercaptan

SH

isopropylmercaptan 2-propanethiol

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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:

Cl + NaHS SH NaCl+

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Thiols Thiols are easily oxidized to disulfides

R SH + R SH R S S RO2

Example for such an oxidation from the biochemistry:

Disulfide bonds are involved in the formation of the tertiary structures of proteins.

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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

OH

+ NaOH

ONa

+ 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 (األصباغ) and plastics

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Phenols Phenol is a standard reference for germicidal

( للجراثيم .(مطهر) activity disinfectants (مبيد Phenol coffecient 5 = 1% desinfectant = 5%

Phenol solution. Cresol (mixture) is a better antiseptic(مطهر)

than phenol but should be used only externally.

OHCH3

OH

CH3

OH

CH3

o-Cresol m-Cresol p-Cresol

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Phenols

OH

OH

CH3

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).

Hexyl resorcinol

OH

O

CH3CH3

CH3OH

CH3CH3

CH3

BHA

BHT

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EthersProperities of ethersNo 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.

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NomenclatureIUPAC: 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.

CH3O CH3

Methoxy propaneMethyl propyl ether

OCH3CH3

Diethyl ether Ethyl ether

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UsesEthylether has been used as anesthetic (مخدر)

for long time (muscle relaxant ( العضالت ,(ارتخاءlittle 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

O FF

Cl

F

F

F

Enflurane

O FF

FCl

FF

Isoflurane