Oxigen containing organic compounds

VII. Alcohols Functional group : -OH Nomenclature: In the IUPAC system, the name of the alkane chain loses the terminal "e" and adds "ol", e.g. "methanol" and "ethanol". When necessary, the position of the hydroxyl group is indicated by a number between the alkane name and the "ol": propan-1-ol for CH 3 CH 2 CH 2 OH, propan-2-ol for CH 3 CH(OH)CH 3. Sometimes, the position number is written before the IUPAC name: 1-propanol and 2-propanol

Methanol Ethanol Propanol Butanol … Naming of alcohols Isomerism1: the position of the -OH group Isomerism 2 : positions of more than one –OH group a. disjunct: -OH groups are not on the same C-atoms b. Germinal : -OH groups are on the same C-atom- VERY UNSTABLE!!!!

tautomerism Tautomers are organic compounds that are interconvertible by a chemical reaction called tautomerization. -this reaction results in the formal migration of a hydrogen atom or proton, accompanied by a switch of a single bond and adjacent double bond. -In solutions where tautomerization is possible, a chemical equilibrium of the tautomers will be reached. The exact ratio of the tautomers depends on several factors, including temperature, solvent, and pH. The concept of tautomers that are interconvertible by tautomerizations is called tautomerism. Tautomerism is a special case of structural isomerism and can play an important role in DNA and especially RNA molecules.

oxo-enol tautomerism OH

Order of alcohols The Order of alcohols depends on the order of carbon atom to which the –OH group is attached Primary alcohol Secondary alcohol Tertiary alcohol ….

Physical properties of alcohols Liquids, because of the –OH group there is a possibility for forming H-bonds Polarity of alcohols Alcohols: bipolar molecules – they have polar and non-polar parts Non-polar polar

Polarity and solubility of alcohols The sorter the Carbon chain the most soluble in water C1 – C3 are soluble in water in every ratio they can make H-bonds because of the –OH group that’s why they have high boiling and melting point Increasing the number of carbon atoms of the alcohols The non polar part will be dominant They are not soluble in water Solubility order: most polar = most soluble in water It’s true for mono alcohols ( only one OH group containing alcohols)

Dialcohols, trialcohols… Polarity and solubility of alcohols If we add one more –OH group the solubility in water and the polarity increasing a lot Factors of solubility of alcohols in water: number of C atoms number of OH groups

Preparation of alcohols Methyl alcohol (methanol) Ethyl alcohol (ethanol) – by biological fermentation Propanol and generally alcohols from: alkenes alcohol oxo compoundsalcohol estersalcohol + carboxylic acid alkyl haloidsalcohol +H 2 O Reduction(+H 2 ) Hydrolysis (+H 2 O) substitution

Chemical properties of alcohols 1. Primary alcohols aldehyde 2. Secondary alcohols R-CH-R R-CO-R ketone oxidation OH Oxidation of :

Other reactions of alcohols: Water eliminations: 1.Intramolecular water elimination with c.c. H 2 SO 4 Alcoholalkene 2. Intermolecular water elimination with % H 2 SO 4 2 Alcoholsether -H 2 O cc H 2 SO 4 H 2 SO 4 -H 2 O

Other reactions of alcohols: 3. Acidity of the alcohols R-CH 2 -OHR-CH 2 -O - + H + Alcoholate ion R-CH 2 -OH + Na+R-CH 2 -O - Na + + H +

Other reactions of alcohols: 4. Ester formation Alcohol + carboxylic acid ester (R 1 -CO-O-R 2 ) Ester formation in 2 steps: 1. nucleophylic addition, 2. elimination of water -H 2 O

Alcohol alkane ( R-CH 3 ) 2 Alcoholether Alcoholalkene Alcohol + aldehyde hemi acetal -H 2 O reduction -H 2 O Other reactions of alcohols:

Alcohol + aldehyde hemi acetal Other reactions of alcohols: -H 2 O Nucleophyllic addition: the attacing agent is the O from the alcohol -OH group Hemi acetal + other alcohol(full) acetal

Other reactions of alcohols: Alcohol + ketone hemi ketal Hemi ketal + alcohol (full) ketal Hemiacetals and hemiketals are generally unstable compounds. In some cases however, stable cyclic hemiacetals and hemiketals can be readily formed. Glucose and many other sugars, for example, exist as a cyclic hemiacetals Acetals are important in nature, for example in solution the most stable form of glucose is its cyclic hemiacetal and maltose is an acetal made from two glucose units.

1. Methanol, CH 3 OH -also known as methyl alcohol, carbinol, wood alcohol -the simplest alcohol, -and is a light, volatile, colourless, flammable, poisonous liquid -Methanol is produced naturally in the anaerobic metabolism of many varieties of bacteria -Methanol is toxic but not directly poisonous. -Methanol is cleaved by the enzyme alcohol dehydrogenase in the liver forming formic acid and formaldehyde which cause blindness by destruction of the optic nerve

2. Ethanol, CH 3 CH 2 OH -also known as ethyl alcohol, drinking alcohol or grain alcohol -flammable, colorless, slightly toxic chemical compound with a distinctive perfume-like odor -In the human body, ethanol is first oxidized to acetaldehyde, and then to acetic acid. - The first step is catalysed by the enzyme alcohol dehydrogenase, and the second by acetaldehyde dehydrogenase. The headache associated with an alcohol hangover stem from a combination of dehydration and acetaldehyde poisoning;

diol or glycol is a chemical compound containing two hydroxyl groups -antifreeze in automobiles and personal computers due to its low freezing point -toxic 3. Ethylene glycol, ethane-1,2-diol

4. Glycerol, also well known as glycerin and glycerine, and less commonly as propane-1,2,3-triol, 1,2,3-propanetriol, 1,2,3-trihydroxypropane, glyceritol, and glycyl alcohol, is a colorless, odorless and sweet-tasting viscous liquid. Glycerol is a sugar alcohol and has three hydrophilic alcoholic hydroxyl groups (OH-) that are responsible for its solubility in water Glycerol is a precursor for synthesis of triacylglycerols and of phospholipids in the liver and adipose tissue. When the body uses stored fat as a source of energy, glycerol and fatty acids are released into the bloodstream. The glycerol component can be converted to glucose by the liver and provides energy for cellular metabolism. Before glycerol can enter the pathway of glycolysis or gluconeogenesis (depending on physiological conditions), it must be converted to their intermediate glyceraldehyde 3-phosphate

5. Long chain alcohols: fatty alcohols More than 10 Carbon in the chain 6. Thio alcohols- O can be substitued by S e.g. thio-ethanol 2Thio ethanols disulfide Thio ethanol sulfonic acid Sulfonic acid general formula RSO 3 H, where R is usually a hydrocarbon side chain Ox –H 2 Ox +H 2

VIII. Ethers Two alkanes are linked via one oxygen atom R-O-R’ The 2 carbons that are bridged by the O they do not contain anything only H Non-polar compounds : C O The EN difference not enough To form H bonds!! – Hydrophobic!!

Nomenclature of Ethers: Trivial names: the name of the two alkyl groups and appending "ether", e.g. "ethyl methyl ether" Dimethyl ether Ethers in general are of very low chemical reactivity VIII. Ethers