Ministry of Higher Education
Salman Bin Abdulaziz University
College of Applied Medical Science
Wadi Addawasir / / المملكة العربية السعودية
وزارة التعليم العالي
جامعة سلمان بن عبدالعزيز
كلية العلوم الطبية التطبيقية
بوادي الدواسر
Department of Applied Medical Lab Science
ORGANIC CHEMISTRY- CHEM- 106, 2nd semester, 2nd level
Academic year: 1433-1434 H / 2012-2013
Ethers:
· Ethers are a class of compound of the general formula R-O-R’.
· R and R’ can be alkyl or aryl. write
Structure
Ethers can be thought of as alkyl analogues of water.
Uses
· Since ethers are relatively unreactive
· Ethers are strongly nonpolar (due to the lone pairs on the oxygen),Ethers are commonly used as solvents for organic reactions.
· For Example: (Diethyl ether ).
Nomenclature of ethers
1. Common names of ethers add the suffix ether after naming the groups on Ether
Physical Properties of ethers
1. At room temperature, ethers are pleasant-smelling colorless liquids.
2. Relative to alcohols, ethers are generally less dense, are less soluble in water, and have lower boiling points.
3. They are relatively unreactive, and as a result they are useful as solvents for fats, oils, waxes, perfumes, resins, dyes, gums, and hydrocarbons.
4. Vapours of certain ethers are used as insecticides, miticides, and fumigants for soil.
5. Ethers are also important in medicine and pharmacology, especially for use as anesthetics.
6. For example, ethyl ether (CH3CH2−O−CH2CH3), simply known as ether, was first used as a surgical anesthetic in 1842.
7. Codeine, a potent pain-relieving drug, is the methyl ether of morphine.
Synthesis of Ether :
1. Williamson synthesis
2. Bimolecular dehydration of Alcohols
Chemical Properties:-Reactions of Ethers
· Typically ethers are stable and chemically inert, although they can undergo two types of reaction (cleavage, oxidation).
1. Cleavage :---Ethers are cleaved by H-Br and H-I, generating the corresponding alkyl halides.
R-O-R’ + excess H-X → R-X + R’-X
Amines
Ammonia
1. Aminesare organic compounds which contain one or more atoms of nitrogen.write
2. Structurally amines resemble ammonia in that the nitrogen can bond up to three hydrogens.
3. In an amine, one or more of the hydrogen atoms from ammonia are replaced by organic substituents like alkyl (alkane chain) and aryl (aromatic ring) groups.
Preparation
The following laboratory methods can be considered to be in common use for purpose of the preparation of amine compounds:
1. The Gabriel synthesis
2. Hofmann degradation of amides
This reaction is valid for preparation of primary amines only, and it gives good yields of primary amines uncontaminated with other amines.
3. Reduction of nitriles and amides
· LiAlH4is more commonly employed for the reduction of nitriles on the laboratory scale.
§ Similarly, LiAlH4reduces amides to amines.
Properties
Types of Amines
· Amines can be eitherprimary,secondaryortertiary, depending on the number of carbon-containg groups that are attached to them.
· If there is only one carbon-containing group (such as in the molecule CH3NH2) then that amine is considered primary.
· Two carbon-containing groups makes an amine secondary, and three groups makes it tertiary.
· Utilizing the lone electron pair of nitrogen, it bind a fourth carbon-containing group to the amine. In this case, it could be called aquaternary ammonium ion.
Primary Amine:/ Secondary Amine:
/ Tertiary Amine:
· An organic compound with multiple amine groups is called adiamine,triamine,tetraamineand so forth, based on the number of amine groups (also calledamino groups) attached to the molecule.
· The chemical formula for methylene diamine (also called diaminomethane), for example, would be as follows: H2N-CH2-NH2
Aromatic amines
Aromatic amines have the nitrogen atom directly connected to an aromatic ring structure.
§ as prefix: "amino-"
§ as suffix: "-amine"
§ the prefix "N-" shows substitution on the nitrogen atom (in the case of secondary, tertiary and quaternary amines)
Systematic names for some common amines:
methylamine
§ Primary amines:ethanamineor ethylamine. write
§ Secondary amines:dimethylamine
§ Tertiary amines:trimethylamine
Physical properties
· As one might readily guess, the inclusion of a heteroatom such as nitrogen in otherwise exclusively carbon and hydrogen molecules has quite an effect on the properties of amines as compared to alkanes.
General properties
· Hydrogen bonding significantly influences the properties of primary and secondary amines as well as the protonated derivatives of all amines.
· Thus the boiling point of amines is generally lower than the corresponding alcohols.
· Most aliphatic amines display some solubility in water, reflecting their ability to form hydrogen bonds.
· Aromatic amines have their lone pair electrons conjugated ("shared") into the benzene ring, so their tendency to engage in hydrogen bonding is somewhat diminished.
Reactions
Amide formation
ü Acyl chlorides and acid anhydrides react with primary and secondary amines without the presence of heat to form amides.
ü Tertiary amines cannot be acylated due to the absence of a replaceable hydrogen atom.
Salt formation
Because amines are basic, they neutralize carboxylic acids to form the corresponding ammonium carboxylate salts. Upon heating to 200°C, the primary and secondary amine salts dehydrate to form the corresponding amides.
Neutralization
Amines R3N react with strong acids such as hydroiodic acid (HI), hydrobromic acid (HBr) and hydrochloric acid (HCl) to give ammonium salts R3NH+.
Reactions with ketones and aldehydes
§ Primary amines react with carbonyl compounds to form imines.
RNH2+ R'2C=O → R'2C=NR + H2O
Use of amines: As drugs
§ Chlorpheniramineis an antihistamine the helps to relief allergic disorders due to cold, hay fever, itchy skin, insect bites and stings.
§ Diphenhydramineis the common antihistamine, benadryl.
§ Chlorpromazineis a tranquillizer that sedates without inducing sleep. It is used to relieve anxiety, excitement, restlessness or even mental disorder.
§ Acetaminophenis also known as paracetamol or p-acetaminophenol, an analgesic that relieves pains such as headaches. It is believed to be less corrosive to the stomach and is an alternative to aspirin.