What are esters? L.O. Know some uses of esters, including natural esters, soaps and biodiesel The Big Fat! Esters have characteristic smells, and are often used in flavourings. For example: propyl ethanoate smells of pears butyl butanoate smells of pineapple methyl butanoate smells of apple. ESTERS Structure
Carboxylic acid Derivative Nomenclature Name first part from alcohol, second part from acid CH3COOCH3 methyl ethanoate METHYL ETHANOATE Smells like glue
METHYL PROANOATE apples ETHYL METHANOATE flavor of raspberries, but smells like rum ESTERS PREPARATION OF ESTERS Esterification or Addition Elimination
Type 1 Alcohol: And Carboxylic Acid CH3CH2OH + CH3COOH CH3COOC2H5(l) + H2O(l) ethanol ethanoic acid ethyl ethanoate water Conc. H2SO4 is a dehydrating agent - it removes water causing the equilibrium to move to the right and thus increases the yield of the ester.
Addition Elimination Type 2 Alcohol: AND Ethyl chloride Equation e.g. CH3OH(l) + CH3COCl(l) CH3COOCH3(l) + HCl(g) methanol ethanoyl methyl chloride ethanoate
Can you give the equation for making rum flavor 2-methylpropylpropanoate? Answer: Propanoic Acid + 2-methylpropanol 2-methylpropylpropanoate + water + H2O FATTY ACIDS Carboxylic acids that are obtained from natural oils and fats; they can be Saturated
9 CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH octadec-9,12-dienoic acid (linoleic acid) Linoleic acid belongs to one of the two families of essential fatty acids, which means that the human body cannot synthesize it from other food components FATTY ACIDS AND HEALTH Saturated solids at room temperature found in meat and dairy products increase cholesterol levels - can lead to heart problems
Mono unsaturated contain just one C=C thought to be neutral to our health found in olives, olive oil, groundnut oil, nuts, avocados Poly unsaturated are considered to be good fats contain more than one C=C bond tend to be liquids at room temperature, eg olive oil. HYDROLYSIS OF ESTERS Hydrolysis is the opposite of esterification Water
OH H HCOOH METHANOIC ACID + ETHANOL ETHYL METHANOATE ESTER + WATER
C2H5OH CARBOXYLIC ACID + ALCOHOL Making Soaps Saponification or Hydrolysis Soaps are formed by the alkaline hydrolysis (breaking up) of fats and oils by sodium or potassium hydroxide ESTER
1,2,3 Propantriol Soap Fatty acids are carboxylic acids with very long carbon chains. The sodium and potassium salts of fatty acids can be used as soaps. For example, reacting octadecanoic acid with sodium hydroxide produces sodium octadecanoate, a common soap. (octadecanoic acid) +
+ (sodium octadecanoate, or SOAP) After the lye (NaOH) has severed the glycerol covalent hydrocarbon chain (there are 3) carboxylate head O- Na+ non-polar, oil-soluble, hydrophobic
O polar, water-soluble, hydrophilic Mechanism of stain/dirt removal Roll-up mechanism The hydrophobic tails burrow into the droplet of oil or grease. The hydrophilic heads are left to face the surrounding water. This results in the formation of a
ball-like structure (a micelle). The non-polar substances, such as oil or grease, are held inside the ball and suspended in water, to be washed away. Soapless detergents When soap is used in hard water, a white solid precipitate we call scum forms. This is because charged calcium and magnesium ions present in the hard water react with soap to form an insoluble substance.
Detergent molecules simply replace the head of the soap -COO - carboxylate group to -SO3- called sulphonate, it is now detergent, not soap. The calcium ions will not ppt with the -SO3- Emulsions Soap for food Ok, yuck, not a soap like in the shower soap, but it has the same ACTION An emulsion contains small droplets of one liquid dispersed in another liquid.
Emulsions in Food Emulsions in food are mixtures of oil and water. To prevent oil and water components separating into layers, a soap-like molecule known as an emulsifier is added. Biodiesel Biofuel: Fuel made from biological ingredients instead of fossil fuels Starting ingredients range from corn to soybeans to animal fat
Non-toxic and renewable Soybean Canola Peanut Why? These compounds contain triacylglycerols, or fat Abbreviated process Transesterification one ester is made from another Fat is reacted with an alcohol, usually methanol. So the glycerol is swapped with the alcohol.
Alcohol for Alcohol (swap) Sodium or potassium hydroxide is used as a catalyst Schematic of the Transesterification process Transesterification one ester is made from another Fat is reacted with an alcohol, usually methanol. So the glycerol is swapped with the alcohol. Alcohol for Alcohol (swap) Sodium or potassium hydroxide is used as a catalyst
Glycerin Uses (the By-Product of Transesterification Uses) Soaps Nitration: produces nitroglycerin Heart disease drug: 0.6 mg Cosmetics
BIODIESEL Final Product Biodiesel 100% Glycerin This. or this? Using US maize to produce ethanol increased tortilla price
in Mexico BioDiesel A better fuel vs. Diesel Benefits Features Greater lubricity Superior detergency Higher flash point
More mileage Greater horsepower Less smoke Smoother running engines Quicker starts
Longer engine life Reduced maintenance Reduced emissions for Biodiesel Emission Component
B100 B20 Total Unburned Hydrocarbons -67% -20% Carbon Monoxide
-48% -12% Particulate matter -47% -12% NOx
+10% +2% Sulfates -100% -20% PAH
-80% -13% Problem: Degrades at rate of four times faster than standard diesel fuel And produces more NOx Biodiesel can gel when it gets cold. Solution: Blend with standard diesel for better cold flow properties History L.O. Know the mechanism of acylation reactions in the manufacture of aspirin Salicin, derived from Willow Bark, had been used since the
time of the ancient Greek philosopher, Hippocrates, to relieve dull aches and pains. In 1897, Felix Hoffman, a researcher from Bayer AG synthesized acetylsalicylic acid from salicin derived from meadowsweet. Aspirin Chemical Structure L.O. Know the mechanism of acylation reactions in the manufacture of aspirin ESTERIFICATION -3 Triangle = Benzoic Acid Circle is 2 Carbons or acetal
The most commonly used acyl group is CH3CO-. (IUPAC ethanoyl ). Esterification-3 Hydroxybenzoic acid. + Ethanoyl Chloride PREPARATION OF ESTERS 3 The Safer Way Equation Notes
CH3OH(l) + (CH3CO)2O(l) > CH3COOCH3(l) + CH3COOH(l) methanol ethanoic methyl ethanoic anhydride ethanoate acid Acid anhydrides are not as reactive as acyl chlorides so the reaction is slower. The reaction is safer - it is less exothermic.
Acid anhydrides are less toxic, no HCL FUMES. Later, in Asprin prep we will see this Acetylation Acetic anhydride forms from 2 acetates or 2 ethanoic acids, it is safer than Ethanoyl Chloride as we avoid the HCl by product Acylation (2 Carbon Addition) of Salicylic Acid
Naming Acid Anhydrides, RCO2COR' If symmetrical replace acid with anhydride based on the related carboxylic acid Ethanoic anhydride Unsymmetrical anhydrides cite the two acids alphabetically Carboxylic Compounds Acyl group bonded to X, an electronegative atom or leaving group Includes: X = halide (acid halides), acyloxys (anhydrides), esters, amides Esterification
Conversion of Acid Halides to Esters Esters are produced in the reaction of acid chlorides. The reaction is better with less steric bulk Biological Oxidation of Alcohols Nicotinamide Adenine Dinucleotide (NAD)
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