ACID HALIDE AND

ACID ANHYDRIDE

An acid halide (also known as an acyl halide) is an organic compound derived from an carboxylic acids by replacing a hydroxyl group with a halide group.

Acid halide

Physical properties of acyl halides An acyl halide such as ethanoyl chloride is a COLORLESS, fuming

liquid. The strong smell of ethanoyl chloride is a mixture of the SMELL

OF VINEGAR (ethanoic acid) and the acrid smell of hydrogen chloride gas.

Solubility in water Acyl halides DO NOT DISSOLVE IN WATER because they react

(often violently) with it to produce carboxylic acids and hydrogen halides

Boiling points Taking ethanoyl chloride as typical: ethanoyl chloride BOILS AT

51°C and Its boiling point is therefore HIGHER THAN AN ALKANE of similar size (which has no permanent dipoles)

Reactivity Acyl halides are EXTREMELY REACTIVE, and in each of their

reactions the halogen atom is replaced by another functional group.

Physical Properties

A common laboratory method for the synthesis of acyl halides entails reaction of carboxylic acids with reagents such as thionyl chloride or phosphorus pentachloride for acyl chlorides, phosphorus pentabromide for acyl bromides and cyanuric fluoride for acyl fluorides.

Aromatic acyl chlorides can be prepared by chloroformylation, a specific type of Friedel-Crafts acylation  using formaldehyde as the reagent.

Preparation

used as intermediates in the synthesis of other organic compounds

Uses

A carboxylic acid such as ethanoic acid has the structure:

If you took two ethanoic acid molecules and removed a molecule of water between them you would get the acid anhydride, ethanoic anhydride (old name: acetic anhydride).

Acid Anhydride

We will take ethanoic anhydride as typical. Appearance Ethanoic anhydride is a COLOURLESS LIQUID,

smelling STRONGLY OF VINEGAR (ethanoic acid). Solubility in water Ethanoic anhydride can't be said to DISSOLVE IN

WATER because it reacts with it to give ethanoic acid.

Boiling point Ethanoic anhydride BOILS AT 140°C. That means

that its boiling point ISN'T AS HIGH AS A CARBOXYLIC

ACID of similar size

Physical properties

Acid anhydrides are used for acetylation in preference to acid halides because the reaction are not as vigorous and are easily controlled.

Acid anhydride is less reactive that is why it is more preferred

Uses

Analgesic and antipyretic Used in the synthesis of sulfa drugs

Structure:

Acetanilide

ESTERSRCOR’ or RCOOR

Carboxylic acid + alcohol: RCOOH + ROH -> RCOOR + HOH Acid halide+ Alcohol RCOX + R’OH -> RCOOR’ HCl

Preparation

Boiling Point: 77.1 ‘C Solubility in water Small esters are fairly SOLUBLE IN WATER

but solubility decreases with increasing chain length.

Physical properties

Banana/pear flavor: acetic acid + isoamyl alcohol

Pineapple flavor: butyric acid + ethyl alcohol

Apple flavor: isovaleric acid + isoamyl alcohol

Rum flavor: formic acid + ethyl alcohol

Artificial Flavors

Plastic balloon: acetic acid + ethyl alcohol Varnishes and lacquers: acetic acid + amyl

alcohol Flowers: acetic acid + methyl alcohol

Odors

Esters that are have fragrant odours are used as a constituent of perfumes, essential oils, food flavourings, cosmetics, etc

Esters are used as an organic solvent Natural esters are found in pheromones Naturally occurring fats and oils are fatty acid esters of

glycerol Phospoesters form the backbone of DNA molecules Nitrate esters, such as nitroglycerin, are known for their

explosive properties Polyesters are used to make plastics Esters are used to make surfactants E.g. soap,

detergents

Uses of Esters

Aspirin *reduces the risk of recurrence of stroke *antipyretic and analgesic Methyl salicylate *liniment *making perfumes and flavor Salol *enteric coating of medicines *intestinal antiseptic

Some important Esters and ester derivatives

Analgesic- drugs that relieve pain w/out the loss of consciousness

Antipyretic- reduces fever Liniment- gentle friction for temporary relief

of pain Enteric coating- coating for medical

preparation

Definition of terms

Spermaceti- largely cetyl palmitate Canauba wax- from Brazilian palm leaves;

used as component of automobile and floor waxes

Beeswax- largely myricyl palmitate; from honeycomb cells

Other esters

SOAP

traditional soap contains OIL AND LYE that have been mixed, and gone through a reaction that unites them. what they do is surround dirt and oil with a bubble of caustic oil, that water is mostly able to wash off. 

detergent, on the other hand, reduces the surface tension of water, so that it (water) surrounds dirt and oil, and washes them away.

Physical properties

 Soaps are mainly used as surfactants for washing, bathing, and cleaning, but they are also used in textile spinning and are important components of lubricants. 

Uses

Usually, a process by which triglycerides are reacted with sodium or potassium hydroxide to produce glycerol and a fatty acid salt, called 'soap'.

What is saponification?

soft soaps tend to dissolve more readily into water, due to the ions of the soap being able to stabilise and disperse into the water.

Hard soaps tends to have ions that make dissolution into water difficult. In other terms, soft soap dissolves easily, where as hard soaps do not.

Difference between hard soap & soft soap

 Detergents are soap-like compounds which are used for cleaning purpose. They are sodium salts of long     chain alkyl benzene sulphonic acids or sodium salts of long chain alkyl hydrogen sulphate, whereas, soaps     are sodium salts of long chain carboxylic acids. The general formulae of soaps and detergents are:

Difference between soap and detergent

When soap is added to water, the ionic-salt end of the molecule is attracted to water and dissolved in it. The non-polar hydrocarbon end of the soap molecule is repelled by water. A drop or two of soap in water forms a monolayer on the water surface as shown in the graphics on the left. The soap molecules "stand up" on the surface as the polar carboxyl salt end is attracted to the polar water. The non-polar hydrocarbon tails are repelled by the water, which makes them appear to stand up. 

Explain the cleansing action of soap