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ACID HALIDE AND ACID ANHYDRIDE
ACID HALIDE AND ACID ANHYDRIDE
An acid halide (also known as an acyl halide) is an organic compound derived from ancarboxylic acidsby replacing a hydroxyl group with a halidegroup.
Physical properties of acyl halidesAnacylhalide such asethanoylchloride is aCOLORLESS,fuming liquid.The strong smell ofethanoylchloride is a mixture of the SMELL OF VINEGAR (ethanoicacid) and the acrid smell of hydrogen chloride gas.Solubility in waterAcyl halides DO NOT DISSOLVE IN WATER because they react (often violently) with it to produce carboxylic acids and hydrogen halidesBoiling pointsTaking ethanoyl chloride as typical:ethanoylchloride BOILS AT 51C and Its boiling point is therefore HIGHER THANANALKANEof similar size (which has no permanent dipoles) ReactivityAcyl 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 ofcarboxylic acidswithreagentssuch asthionyl chlorideor phosphorus pentachloridefor acyl chlorides,phosphorus pentabromidefor acyl bromides andcyanuric fluoridefor acyl fluorides.Aromaticacyl chlorides can be prepared bychloroformylation, a specific type ofFriedel-Crafts acylation usingformaldehydeas the reagent.
used as intermediates in the synthesis of other organic compoundsUses
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).
We will take ethanoic anhydride as typical.AppearanceEthanoic anhydride is a COLOURLESS LIQUID, smelling STRONGLY OF VINEGAR (ethanoic acid).Solubility in waterEthanoic anhydride can't be said to DISSOLVE IN WATER because it reacts with it to give ethanoic acid. Boiling pointEthanoic anhydride BOILS AT 140C. That means that its boiling point ISN'T AS HIGH AS A CARBOXYLIC ACID of similar sizePhysical 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
Analgesic and antipyreticUsed in the synthesis of sulfa drugs
ESTERSRCOR or RCOOR
Carboxylic acid + alcohol: RCOOH + ROH -> RCOOR + HOHAcid halide+ Alcohol RCOX + ROH -> RCOOR HCl
Boiling Point: 77.1 CSolubility in waterSmall esters are fairly SOLUBLE IN WATER but solubility decreases with increasing chain length.
Banana/pear flavor: acetic acid + isoamyl alcoholPineapple flavor: butyric acid + ethyl alcoholApple flavor: isovaleric acid + isoamyl alcoholRum flavor: formic acid + ethyl alcoholArtificial Flavors
Plastic balloon: acetic acid + ethyl alcoholVarnishes and lacquers: acetic acid + amyl alcoholFlowers: acetic acid + methyl alcoholOdors
Esters that are have fragrant odours are used as a constituent of perfumes, essential oils, food flavourings, cosmetics, etcEsters are used as an organic solventNatural esters are found in pheromonesNaturally occurring fats and oils are fatty acid esters of glycerolPhospoesters form the backbone of DNA moleculesNitrate esters, such as nitroglycerin, are known for their explosive propertiesPolyesters are used to make plasticsEsters are used to make surfactants E.g. soap, detergents
Uses of Esters
Aspirin *reduces the risk of recurrence of stroke *antipyretic and analgesicMethyl salicylate *liniment *making perfumes and flavorSalol *enteric coating of medicines *intestinal antiseptic Some important Esters and ester derivatives
Analgesic- drugs that relieve pain w/out the loss of consciousnessAntipyretic- reduces feverLiniment- gentle friction for temporary relief of painEnteric coating- coating for medical preparation
Definition of terms
Spermaceti- largely cetyl palmitateCanauba wax- from Brazilian palm leaves; used as component of automobile and floor waxesBeeswax- largely myricyl palmitate; from honeycomb cellsOther esters
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 assurfactantsforwashing,bathing, andcleaning, but they are also used in textile spinning and are important components oflubricants.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 oflong 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