OXYGEN CONTAINING ORGANIC COMPOUNDS Compounds of oxygen q

OXYGEN CONTAINING ORGANIC COMPOUNDS

Compounds of oxygen q Carbohydrates, fats, proteins, nucleic acids are complex molecules containing oxygen. q First is necessary to study simpler organic compounds: q Alcohols, phenols, ethers, aldehydes, ketones, acids, esters.

Electron configuration of oxygen atom: 1 s 2 2 p 4 In organic molecule oxygen is attached covalently with two pairs of atoms O O

q Alcohols and phenols (hydroxy derivates) – compounds with the hydroxyl (-OH) R-O-H q Ethers – compounds with alcoxyl group (-OR) R-O-R

q Aldehydes and ketones – carbonyl group - C= O R C= O H q R R - C=O Carboxylic acids – carbonyl + hydroxyl group R H -O - - C = O-

Alcohols

Alcohols Classification In 1 o alcohol, only one carbon atom is attached to the carbon carrying the -OH group (primary carbon). q In 2 o alcohol two carbon atoms are attached to the carbon carrying the -OH group (secondary carbon). q In 3 o alcohol three other carbon atoms are attached to the carbon atom carrying the -OH group (tertiary carbon). q

Alcohols The number of hydroxyl groups, there are: Monohydroxyderivatives (monohydroxy alcohols) Polyhydroxy alcohols q Diols (dihydroxyderivatives, ) q q q Triols (trihydroxyderivatives) Tetrols (tetrahydroxyderivatives) Polyols belongs to a group of carbohydrates (sugars) Phenols -OH attached primary to aromatic ring

Nomenclature of Alcohols The lower molecular weight alcohols have common names. Word alcohol is added after the name of the alkyl group to which the hydroxyl group is attached. methanol – methyl alcohol ethanol – ethyl alcohol 1 -propanol – propyl alcohol 2 -propanol – isopropyl alcohol 1 -butanol – n-butyl alcohol CH 3 -OH CH 3 -CH 2 -CH 2 -OH CH 3 -CH-CH 3 OH CH 3 -CH 2 -CH 2 -OH

Properties Low MW alcohols are colorless liquids of specific odour (unpleasant from C 4), narcotic effect, toxic. q q Polyhydroxy alcohols have sweet taste. q Higher alcohols (from C 12) are solid compounds H-bonds → solubility in water, higher boiling points than alkanes. q

Reaction of Alcohols 1. Braking the oxygen-hydrogen bond. H H C C An acid-base reaction. O H 2. Braking the carbon-oxygen bond. H H C C A substitution reaction by a nucleophile. O H

Reaction of Alcohols 3. Braking both the oxygen-hydrogen bond and the carbonhydrogen bond at the carbon atom bearing the -OH group. An oxidation reaction. H H C C O H 4. Breaking both the carbon-oxygen bond and the carbonhydrogen bond at a carbon atom adjacent to the carbon atom bearing the –OH group H H C C An elimination reaction. O H

Reaction of Alcohols The –OH group generally makes the alcohol molecule polar. q The -OH group can form hydrogen bonds to one another and to other compounds. q q Alcohols, like water, act as acids or bases http: //en. wikipedia. org/wiki/Alcohol#Physical_and_chemical_properties

Dehydratation of Alcohols n n Alcohols undergo combustion with O 2 to produce CO 2 and H 2 O. 2 CH 3 OH + 3 O 2 2 CO 2 + 4 H 2 O + Heat Dehydration removes H- and -OH from adjacent carbon atoms by heating with an acid catalyst. H OH | | H+, heat H—C—C—H H—C=C—H + H 2 O | | H H alcohol alkene

Dehydratation of Alcohols Ethers form when dehydration takes place at low temperature. q H+ CH 3—OH + HO—CH 3 Two methanol CH 3—O—CH 3 + H 2 O Dimethyl ether

Oxidation of Primary Alcohols q In the oxidation [O] of a primary alcohol, one H is lost from the –OH and another H from the carbon bonded to the OH. [O] Primary alcohol OH | CH 3—C—H | H Ethanol (ethyl alcohol) Aldehyde [O] O || CH 3—C—H + H 2 O Ethanal (acetaldehyde)

Oxidation of Primary Alcohols Aldehydes can easily be oxidized to produce acids q Aldehyde [½ O 2] O || CH 3—C—H Ethanal (acetaldehyde) [½ O 2] Carboxylic acid O || CH 3—C—OH Acetic acid

Oxidation of Secondary Alcohols q The oxidation of a secondary alcohol removes one H from –OH and another H from the carbon bonded to the –OH. [O] Secondary alcohol OH | CH 3—C—CH 3 | H 2 -Propanol (Isopropyl alcohol) Ketone [O] O || CH 3—C—CH 3 + H 2 O Propanone (Dimethylketone; Acetone)

Oxidation of Tertiary Alcohols q Tertiary alcohols are resistant to oxidation. [O] Tertiary alcohols no reaction OH | [O] CH 3—C—CH 3 no product | CH 3 no H on the C-OH to oxidize 2 -Methyl-2 -propanol

Production q Methanol Obtained by heating wood to a high temperature in the absence of air. q Toxic substance, temporary blindness (15 ml), permanent blindness or death (30 ml) q

Production q Ethanol (spiritus, alcohol) Obtained by fermentation from sugar juices q Fermentation from sugar from the hydrolysis of starch in the presence of yeast and temperature of less than 37°C q C 6 H 12 O 6 (hexose) 2 CH 3 CH 2 OH + 2 H 2 O q Acts as a depressant. q Lethal dose is 6 -8 g/kg ( 1 L of vodka)

Oxidation of Alcohol in the Body q q Enzymes in the liver oxidize ethanol to acetaldehyde The aldehyde produces impaired coordination. Ethanol acetaldehyde acetic acid Oxidation of methanol in the liver produces formaldehyde CH 3 OH H 2 C=O

Ethanol – An Antidote for Methanol Poisoning Formaldehyde reacts very rapidly with proteins. q Enzymes loss of the function. q Ethanol competes for the oxidative enzymes and tends to prevent the oxidation of the methanol to formaldehyde. q

Polyhydroxy Alcohols Ethylene glycol - ethane-1, 2 -diol HO–CH 2–OH q q Used as a radiator and automobile antifreez toxic: 50 m. L, lethal: 100 m. L Glycerol - propane-1, 2, 3 -triol (glycerin) CH 2 - OH q Present as the backbone of several important biological compounds

Glycerol n n Oxidation of glycerol arises glyceraldehyde – major metabolite. Reaction with acid esters formed - with nitric acid arises glyceroltrinitrate – nitroglycerin. Nitroglycerin is administered as a treatment for heart disease.

Glycerol n n The phosphoric acid esterifies primary –OH group to form 1 -glycerophosphate acid is an important metabolite and a structural component of complex lipids.

Glycerol as a Beckbone for Several Bilogical Compounds phosphatidylcholine phosphatidylethanolamine

Phenols Class of chemical compounds consisting of a hydrohyl group (-OH) bonded directly to an aromatic hydrocarbon group. q Phenol

Phenols with a single hydroxyl group, meaning mono hydroxyl phenols q Phenols with more than one hydroxyl groups in the molecule, meaning poly hydroxyl phenols q Dihydroxybenzenes Components of biochemical molecules

Physical Properties of Phenols polar, can form hydrogen bond q water insoluble q stronger acids than water and will dissolve in 5% Na. OH q weaker acids than carbonic acid q Methyl derivatives - cresols are used to dissolve other chemicals, as disinfectants and deodorizers, and to make specific chemicals that kill insect pests.

Reactivity of Alcohols and Phenols Reaction with carboxylic acids, acid chlorides and acid anhydrides to form esters. q Reaction of primary or secondary alcohol in the presence of a catalyst (commonly concentrated sulfuric acid) with carboxylic acid is called esterification. q The introduction of acetyl (CH 3 CO-) group in alcohols or phenols in known as acetylation. q

Ethers

Ethers Derivatives of water q An oxygen atom connected to two alkyl or aryl groups q Diethylether CH 3 -CH 2 -O-CH 2 -CH 3 Solvent and anestetic

Properties Ether molecules cannot form hydrogen bonds amongst each other, resulting in a relatively low boiling point compared to that of the analogous alcohols. q Ethers are slightly polar. q

Aldehydes and Ketones

Aldehydes and Ketones q Aldehydes and ketones have carbonyl group C=O Aldehydes have the carbonyl carbon atom bonded to at least one hydrogen atom. q Ketones have the carbonyl carbon atom bonded to two other carbons. q

Formaldehyde Methanal Glyoxal Ethandial Acetaldehyde Ethanal Benzaldehyde Propionaldehyde Propanal Akrylaldehyde Propenal Cinnamaldehyde 3 -phenyl propenal Acetone propanone Acetophenone Methylphenyl ketone Ethylmethyl ketone Butanone Cyclohexanone Benzophenone Diphenyl ketone

Formation of Hemiacetals and Hemiketals An alcohol addition reversibly to an aldehyde or ketone produce hemiacetal or hemiketal and –OH group and OR 1 group are attached to the same carbon. q Hemiacetal hydroxyl Hemiacetals are unstable. q Sugars contain both –OH and C=O groups that undergo these reactions. q

The family of aldose The family of ketose

Hemiacetal Formation 1. The electrons on the alcohol oxygen are used to bond the carbon #1 to make an ether (red oxygen atom). 2. The hydrogen (green) is transferred to the carbonyl oxygen (green) to make a new alcohol group (green). http: //www. elmhurst. edu/~chm/vchembook/700 carbonyls. html

Hemiketal Formation 1. The electrons on the alcohol oxygen are used to bond the carbon #2 to make an ether (red oxygen atom). 2. The hydrogen (green) is transferred to the carbonyl oxygen (green) to make a new alcohol group (green). http: //www. elmhurst. edu/~chm/vchembook/700 carbonyls. html

Reactions of Aldehydes and Ketones with Amines Aldehydes and ketones react with primary amines to form imines, or Schiff bases (sugars with proteins, neenzymatic glycation in diabetes).

Carboxylic Acids

Carboxylic Acids R-COOH q Functional group is carboxyl group. R – can be alifatic chain (CH 3 CH 2 -), cyclic molecule (including heterocycle) or aromatic molecule, exceptionally hydrogen (HCOOH). q q Involved in many vital function. q Cleavage of H+ allows the formation of salts.

Examples of monocarboxylic acids Formic acid Methanoic acid Stearic acid Octadecanoic acid Acetic acid Ethanoic acid Oleic acid Cis-9 -octadecanoic acid Propionic acid Propanoic acid Butyric acid Butanoic acid Isobutyric acid Isobutanoic acid Valeric acid Pentanoic acid Palmitic acid Hexadecanoic acid Acrylic acid Propenoic acid Crotonic acid trans-2 -butenoic acid Benzencarboxylic acid b-naphtoic acid 2 -naphtalenecarboxylic acid

Examples of Polyfunctional Carboxylic Acids Dicarboxylic acids HOOC-COOH – oxalic acid HOOC-CH 2 -COOH – malonic acid HOOC-CH 2 -COOH – succinic acid (citric cycle) HCCO-CH 2 -CH 2 -COOH – glutaric acid -OH group containing acids lactic acid malic acid citric acid Ketoacids Unsaturated acids pyruvic Maleic acid and fumaric acid are geometric isomers oxaloacetic acid a-ketoglutaric acid

Properties The liquid carboxylic acids (low molecular weight) have sharp and unpleasant odors (butyric acid occurs in rancid butter and aged cheese). q Liquid at room temperature. q The high molecular weight acids (myristic, palmytic, stearic) are known as fatty acids. q Wax-like solids q

Acidic Properties of Carboxylic Acids q Carboxylic acids are week acids. Partially dissociate into H+ cationts and RCOO - anionts in the water. q CH 3 COOH CH 3 COO - + H+ CH 3 COOH + OH− CH 3 COO− + H 2 O

Salts of Carboxylic acids react with bases to produce carboxylate salts. q The name of salt is derived from acid name by changing –ic ending to –ate and preceding the name with the name of the methal ion (sodium acetate or sodium ethanoate). q

Acetylation of salicylic acid produces aspirin, which possesses analgesic, anti-inflammatory and antipyretic properties.

Esters of Carboxylic Acids Carboxylic acids can react with an alcohol to form an esters Esters have a pleasant odor. q The aroma of many flowers, fruits, and perfumes are due to a mixture of esters. q

Esters Used as Flavoring Agents