Alcohols, phenols &ethers

Alcohols and phenols may be viewed as organic derivatives of water. Alcohols and phenols have a common functional group, the hydroxyl group, —OH.   Alcohols, and Phenols In alcohols the hydroxyl group is attached to an alkyl group, —R. In phenols the hydroxyl function is attached to an aromatic ring, Ar.   Alcohols are classified into:  Classification and Nomenclature of Alcohols

1. Select the longest continuous carbon chain that contains OH group. Replace the ending the suffix -ol. IUPAC Name 2. If a molecule contains both an -OH group and a C=C or C≡C triple bond. - The name should include both the hydroxyl and the unsaturated groups. - If a compound contains both OH and a double or triple bond, choose the chain that include them both even if this is not the longest chain. - The -OH group takes preference before the double or triple bonds in getting the lower number. -

3. In the IUPAC system. The suffix diol is added to the name of the parent hydrocarbon when there are two OH groups. triol is added when there are three OH group 4- Cyclic alcohol, no. starts from C near to OH Two OH groups on adjacent carbons are known as 1,2-glycols.

Primary alcohol CH 3 OH CH 3 CH 2 OH CH 2 =CHCH 2 OH Common Methyl alcohol Ethyl alcohol Allyl alcohol IUPAC Methanol Ethanol 2-Propen-1-ol Secondary and tertiary alcohol Common name listing the alkyl substitutents attached to the hydroxyl group, followed by the word alcohol.

Physical Properties of Alcohols As the number of carbons in the alcohol increases, the solubility in water decreases. when No. of OH  Soluble. in H 2 O  inc. The Increase of alcohol BP. is due to the presence of hydrogen bonding The boiling points increase with increase in molecular weights. Triols Diols and are more soluble in water than monohydroxy alcohols. Solubility Boiling points BP. In straight chains is higher than branched

Alcohols are week acids. In isomer BP. Dec. with  in alkyl gp. 3  < 2  <1  alcohol BP. Higher than it is alkanes ( hydrogen bond) Alcohol weaker acids than phenol and carboxylic acids

Synthesis (Preparation) of Alcohols 1. From alkene. Cis H2OH2O

2– From alkyl halid

3] From reduction of aldehyd, ketones & carboxylic acid: (Reduction of aldehyde and ketone for preparing 1  & 2  alcohol only not 3  ) Reducing agent : - Zn / H +, Zn / HCl, Na / alcohol, NaBH 4 /H 2 O ( for aldehyd or keton.) -H 2 / Pt or Pd or Ni, (all=) - Li Al H 4 /dry ether (all C=O) 1 22 11

4] From Grignard reagent: for (1 , 2  & 3  ) a) with aldehyde : b) with ketones: 2

-Alcohols doesn't react with strong bases (only with metal ) 1- Salt and Ester Formation (Dissociation of O-H Bond) : 2-Dehydration (Elimination Reactions) : 222 Reactions of Alcohols

3] Oxidation: 1  & 2  only 1  with weaker oxidizing agent aldehyde 1  with strong oxidizing agent carboxylic acid 3  alcohol no reaction

4] Reaction with alkyl halides (Substitution Reaction) :

Phenols is an hydroxyl group attached directly to a benzene ring Nomenclature and acidity of Phenols e ol Phenols are generally named as derivatives of the simplest member of the family, phenol.

Acidity of Phenols Introduction of electron-withdrawing groups, such as NO 2 or CN, on the ring increases the acidity of phenols. Alcohols and phenols have weak acidic properties. Phenols are much stronger acids than alcohols. Introduction of electron-withdrawing groups, such as NO 2 or CN, on the ring increases the acidity of phenols. (NO 2 ) is e with. (deact.gp) acidity (CH 3 )is dona.gp. acidity

Preparation of phenols 1-From Diazonium salts: 2-From alkali fusion of sodium benzene-sulfonates:

Reactions of Phenols EWilliamson ether synthesis EEster formation

2-Reaction of aromatic nucleus of phenol (Electrophilic Substitution) CCl 4 EHalogenation

E Salt formation via strong base or active metal E Williamson ether synthesis E Ester formation E Friedel-Crafts acylation: Fries rearrangement E Halogenation E Coupling with diazonium salts E Kolbe-Schmitt Carboxylation E Reimer-Tiemann reaction

EFriedel-Crafts acylation: Fries rearrangement EWilliamson ether synthesis EEster formation ECoupling with diazonium salts EKolbe- Schmitt Carboxylation EReimer- Tiemann reaction ESalt formation via strong base or active metal

Reimer-Tiemann Reaction Mechanism

ETHER

Structure and nomenclature of ethers Ethers are compounds of formula R -0-R', where R and R' may be alkyl groups or aryl (benzene ring) groups. Common names (Alkyl Alkyl Ether Names) Common names of ethers are formed by naming the two alkyl groups on oxygen and adding the word ether. Under the current system, the alkyl groups should be named in alphabetical order.

Common: Diphenyl ether IUPAC : Phenoxy benzene Common : Methyl Phenyl ether (anisole) IUPAC : Methoxy benzene 3-Methoxyhexane 5-Ethoxy-2-heptene 1-Phenoxy-1-propene

Physical Properties of Ether Solubility in water  Ethers are much less soluble in water than alcohols.  More water-soluble than hydrocarbons of similar molecular weight. compoundFormulaMWBp (°C) ethanolCH 3 -CH 2 -OH4678 Dimethyl etherCH 3 -O-CH propaneCH 3 -CH 2 -CH Boiling Points The boiling points of ethers are lower than those of alcohols having the same molecular weights

The dehydration of alcohols takes place in the presence of acid catalysts (H 2 SO 4, H 3 PO 4 ) under controlled temperature. The general reaction for ether formation is: Examples Preparation of ethers 1]Dehydration of alcohols

2]The Williamson synthesis of ethers R-OH + Na (metal) R-O-Na ( sod. Alkoxid)+ H 2 Sod. alkoxides + organic halides (1  &2  ) )--- ether (sy. &unsy.) t-Butyl methyl ether Ethyl phenyl ether Methyl Phenyl ether (anisole)

The alkoxide is commonly made by adding Na or K to the alcohol Examples 3,3-dimethyl-2-pentanol2-ethoxy-3,3-dimethypentane Alkoxide from alcohol

 When ethers are heated in concentrated acid solutions, the ether linkage is broken.. Reaction of Ether 1) Cleavage of ethers by hot concentrated acids General equation: If an excess of acid i s present, the alcohol initially produced is converted into an alkyl halide by the reaction.

Epoxides are cyclic ethers in which the ether oxygen is part of a three-membered ring.  The simplest and most important epoxide is ethylene oxide. Cyclic Ethers (Epoxide)

Peroxy acids (sometimes called per acids) are used to convert alkenes to epoxides. If the reaction takes place in aqueous acid, the epoxide opens to a glycol. Because of its desirable solubility properties, meta-chloroperoxybenzoic acid (MCPBA) is often used for these epoxidations. Peroxy acid Epoxidation: Example: Synthesis of Cyclic ether

 Their reactivity is due to the strain in the three-membered ring, which is relieved when the epoxide ring is opened after a reaction has taken place.  Examples of ring-opening reactions of ethylene oxide that form commercially important products are: 1- Epoxides open in acidic solutions to form glycols. Reaction of Epoxides 2- Epoxides open in acidic alcohol solutions to form 2-alkoxy alcohols.

3- When an epoxide reacts with a hydrohalic acid ( HCl,HBr, or HI), a halide ion attacks the protonated epoxide. 4- Reactions of Epoxides with Grignard and Organolithium Reagents