Part 6. The chemistry of carboxylic acids and their derivatives.
Doc Brown's Advanced Level Pre-University Chemistry Review Study Notes for UK Advanced Level Organic Chemistry Students KS5 A/AS GCE IB US K12 Class 11 Class 12 Organic Chemistry Preparation and Uses of Esters, Balanced Equations, devices, reagents, use as solvents, in Perfumes and Fragrances
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This is a BIG website, you should take your time exploring it [SUCH BOX]6.8 Esters - Preparation, physical and chemical properties and uses, including transesterification (transesterification), solvents and fragrances
Subscript for this page
6.8.1Process for the production of esters - esterification
6.8.2Physical properties of esters.
6.8.3Hydrolysis of esters with acid or base
6.8.4Transesterification of esters (exchange of the acid or alcohol component)
6.8.5use of esters(See alsoPart 6.14 also overlaps)
For basic IGCSE/GCSE review notes, seeEsters, chemistry and applications including fragrances, solventsand more information and links can be found on this page for advanced students of organic chemistry.
See also 6.9Natural esters - triglyceride fats and oils, margarine and biodiesel production
For polyester see section 6.10The manufacture, molecular structure, properties and uses of polyesters.
Three questions based on the formulas and nomenclature of esters
Q1.Name the given esters using their basic formulas and draw the abbreviated structural formulas
Q2.Name the given ester compounds using their abbreviated structural formulas and draw their basic formula.
Q3Extract the skeletal formula and the abbreviated structural formula of the first name
6.8.1Process for the production of esters.
As a reminder, an ester here is a chemical compound made up of an organic acid and an alcohol/phenol. where at least one -OH-hydroxyl group of the organic acid is replaced by an -O-alkyl(alkoxy)/aryl group, for example, as in the esterification substitution reaction of a carboxylic acid and an alcohol.
In principle, the reaction equations for the two methods described here are:
(a) alcohol/phenol + carboxylic acid ===> ester + water
This reaction is detailed on this page and elsewhere too!
(b) alcohol/phenol + acid chloride ===> ester + hydrogen chloride
This reaction is also described in Section 6.7A.
Reactions of acid chlorides also with alcohols/phenols
(c) alcohol/phenol + acyl(acid) anhydride ===> ester + carboxylic acid
This reaction is also described in Section 6.7B.
Reactions of acyl acids/anhydrides also with alcohols/phenols
name ester
The first part of the ester name is derived from alcohol or phenol, e.g. methyl, ethyl, phenyl.
The second part of the name derives from carboxylic acid, for example... oats or... carboxylate.
Examples are given in the following table in Section 6.8.2.
When writing the shorthand formula, the opposite is "generally" true, so be careful!
Ver
Brief descriptions of preparation methods with equations
(a) Carboxylic acid esters plus alcohol using an acid catalyst
This esterification method is also an example ofcondensation reaction- Two molecules combine to form a larger molecule, separating a small molecule, in this case water.
Concentrated sulfuric acid acts as a catalyst in this reaction.
General verbal equation for esterification:
carboxylic acid + alcohol == acid catalyst ==> ester + water
z.B.acetic acid + ethanol
sometimes written easier than
CH3COOH + CH3CH2OH
the reaction isreversibleand the mixture is enoughbalance, and only approx. 2/3Portions of the carboxylic acid and alcohol were converted to the ester..
without astrong acid catalysteg concentrated sulfuric acid, the reaction is very slow and the mixture is heated to further increase the rate of reaction (see procedure details below).
See another page for a full description of how to make an ester like ethyl ethanoate.
It's easy to do a simple lab demo
mix a few cm3(~2:1 ratio) small amounts of acetic acid and butan-1-ol with an even smaller amount of concentrated sulfuric acid (6 drops is enough).
(Video) Grignard Reagent Reaction MechanismThe mixture is gently heated in a beaker of warm water for 5 to 10 minutes.
Do not overheat if the boiling point of the ester is below 100oC.
+
+H2o
acetic acid + butan-1-ol
CH3COOH + CH3CH2CH2CH2OH
The mixture is then poured into a beaker containing a bicarbonate of soda solution.
The baking soda neutralizes the acid catalyst and any unreacted "smelly" carboxylic acids. Excess alcohol should also be dissolved in the water.
You should leave a few drops of ester on the surface that you can smell gently to appreciate the aroma of the ester, which should have a fruity odor.
You can do this as a good class experiment with various alcohols and acetic acid, much less rancid than butanoic acid, as long as you don't mind a big vinegar smell!
Find out what the students think the esters (probably “fruity”) smell like and guess their molecular structure too!
Repeating the experiment with butanoic acid (initially rancid odor) and ethanol yields ethyl butanoate, which also smells like pineapple and is used as a flavor enhancer in processed orange juices.
CH3CH2CH2COOH + CH3CH2OH
The Mechanism of Acid Catalyzed Esterification(simplified)
for example, the formation of ethyl ethanoate with conc. sulfuric acid as a catalyst
CH3COOH + CH3CH2OH
(i) The acid protonates the carboxylic acid
CH3COH + H2SO4===> [CH3COH2]++ HSO4-
(ii) The protonated carboxylic acid decomposes into an acylium cation
[CH3COH2]+===> [CH3CO]++H2o
(iii) The alcohol molecule donates an electron pair to the acylium ion, the ester molecule is formed, and at the same time, the hydrogen sulfate ion releases and accepts a proton to reform the sulfuric acid molecule catalyst.
[CH3CO]++CH3CH2OH ===>CH3KOCH2CH3+H+
H++ HSO4-===> h2SO4
(b)Reaction between an acid/acyl chloride and an alcohol
Acyl chloride and alcohol usually react rapidly at room temperature, especially when both are aliphatic..
Examples of nucleophilic addition of an alcohol to an acid/acyl chloride followed by elimination to the ester and hydrogen chloride.
(YO)Etanoilcloruro + Etanol ===> Etiletanoato + Chlorwasserstoff
(ii)Ethanoylchloruro + Phenol ===> Feniletanoato + Chlorwasserstoff
(iii)Pentanoilcloruro + Propan-1-ol ===> Propilpentanoato + Chlorwasserstoff
In contrast to the ~67% yield of the acid catalyzed esterification described in method (a), this reaction gives a very high yield of >90%.
For more details and mechanisms see6.7
(C)Reaction between an acyl acid/anhydride and an alcohol
(RCO)2O + 2R'OH ===> RCOOR' + RCOOH (R = Alkyl or Aryl, R' = Alkyl)
The reaction is called acetic anhydride.ethanolation- a special case of acylation, addition of a CH3-C=O group in a molecule.
for example, acetic anhydride + ethanol ===> ethyl ethanate + acetic acid
y
pentanoic anhydride + propan-1-ol ===> propyl pentanoate + pentanoic acid
This reaction is also described in Section 6.7B.
Reactions of acyl acids/anhydrides also with alcohols/phenols
+CH3-CH2-OH ===>
===>
+ HCl
TOP OF PAGE and subscript
6.8.2Physical properties of esters.
The lower representatives of the esters of aliphatic acids are colorless liquids with relatively low boiling points at room temperature.
Some of the lower bonds are readily soluble in water, but most are insoluble or sparingly soluble.
Table with abbreviated structural formula and boiling point inoC, further notes on water solubility and isomerism.
Table of names, abbreviated structural formula and boiling point inoC. | |||
| abbreviated formula | Name | Boiling point | Observations |
| 1. HCOOCH3 | Methyl methanoate | 31 | Very soluble in water. |
| 2. CH3KOCH3 | methyl ethanoate | 57 | Moderately soluble in water. |
| 3. HCOOCH2CH3 | ethyl methanoate | 54 | Sparingly soluble in water, the second and third are isomers. |
| 4. CH3KOCH2CH3 | Ethyl ethanolate | 77 | Easily soluble in water. |
| 5. HCOOCH2CH2CH3 | of propyl methanoate | 81 | Slightly soluble in water, the fourth and fifth are isomers. |
| 6.CH3CH2CH2KOCH2CH2CH3 | propyl butanoate | 143 | Very slightly soluble in water. |
| 7.CH3CH2KOCH2CH2CH2CH3 | butyl propanoate | 146 | Very slightly soluble in water, isomers 6 and 7 are isomers |
| 8. C6H5COOK6H5 | fenilbenzoato | 314 | Insoluble in water, melting point 71oC. |
Additional notes and comments on the information table above.
(i) Ester isomers tend to have similar boiling points and solubilities and have similar polarity.
With the same number of electrons in the molecule, they have similar intermolecular forces, mainly instantaneous dipole, induced dipole plus permanent dipole, permanent dipole attractive forces.
They are polar molecules, but the boiling points of esters (RCOOR) are much lower than those of isomeric carboxylic acids, which can form hydrogen bonds between RCOOH (R = alkyl or aryl) molecules.
There are no hydrogen bonds between the ester molecules.
(ii) Although they are polar molecules, they generally have low solubility in water because they cannot form strong hydrogen bonds with water.
(Video) Alkene + KMnO4 ReactionThe lower first members are quite or very soluble in water, but as the length of the molecule increases, too many hydrogen bonds are broken between the water molecules without compensating for the intermolecular attractions between the solute and the solvent, so the solubility decreases rapidly as the carbon chain length increases.
The solubility of the lower limbs in water is attributed to their polar nature AND they can accept the donation of hydrogen bonds from water molecules (which are often not mentioned in textbooks).
Hydrogen bond between an ether and a water molecule:R2Ö:d-IIId+HOH
(iii) Alternative names
Propyl butanoate may also be referred to as 1-propyl butanoate to distinguish it from the structural isomer
CH3CH2CH2COOCH(CH3)2, which may be referred to as 2-propyl butanoate (1-methylethyl butanoate).
Smell – smell – smell!
Esters tend to have pleasant odors and are used in flavors and fragrances and occur naturally in many plants.
TOP OF PAGE and subscript
6.8.3Hydrolysis with acid or alkali: the opposite of esterification
Esters can be hydrolyzed by reflux with strong mineral acids or alkalis.
Hydrolysis is very slow with pure water, much faster with dilute mineral acid (HCl(aq) or H2SO4(aq)) and even faster with a strong base (NaOH (aq) or KOH (aq/ethanol).
The reaction is the opposite of esterification.
(a)Hydrolysis of an ester with dilute hydrochloric or sulfuric acid
RCOOR' + H2o
This reaction cannot go to completion because it is a reversible reaction., despite using a catalyst and reflowing the mixture.
You can get a high percentage yield using an aqueous solution with copious amounts of excess water.
z.B.butyl propanoate + water
CH3CH2KOCH2CH2CH2CH3+H2o
(b)Hydrolysis of an ester with aqueous sodium hydroxide
hydrolyze an esterwith a strong base, for example, called aqueous or ethanolic sodium/potassium hydroxideVerseifung, that is, it is a specific name for aspecial type of hydrolysis reaction.
This strongly basic method of hydrolysis is much faster than water and also faster than acid catalysis.
RCOOR' + NaOH===> RCOONa + R'OH
RCOOR' + OH-===> RCOO-+ R'OH
for example, using the same ester as in (a) thereforeirreversible reaction...
z.B.Butyl propanoate + Sodium hydroxide===> Sodium propanoate + Butan-1-ol
CH3CH2KOCH2CH2CH2CH3+ NaOH ===> NUR3CH2COONa + NUR2CH2CH2CH3OH
CH3CH2KOCH2CH2CH2CH3+ OH-===>CH3CH2GURREN-+CH2CH2CH2CH3OH
This reaction is not reversible and proceeds 100% to form the sodium salt of the acid.
The carboxylic acid is released by adding an excess of strong sulfuric or hydrochloric mineral acid.
z.B.RCOONa + HCl ===> RCOOH + NaCloRCOO-+H+===> RCOOH
CH3CH2COONa + HCl ===> CH3CH2COOH + NaCl
CH3CH2COONa + H+===>CH3CH2COH
Note on hydrolysis andSOAPmanufacturing
What is? How is it done? and it's another use of esters!
'Traditional'soap is aProduct of the hydrolysis of animal fats and vegetable oils.
You reflux the fat or vegetable oil with aqueous sodium hydroxide.
"Soap" soaps (not modern "soapless" detergents) are sodium salts of long-chain fatty acids formed by heating fixed oils with concentrated alkalis such as sodium hydroxide or potassium hydroxide to hydrolyze them.
This is known asVerseifungsreaktionand a typical equation is shown above and the word general equation is quoted below.
Vegetable oil/animal fat + sodium hydroxide ==> soap molecule + glycerin
In the example illustrated above, the saponification (hydrolysis) product is sodium soap palmitate.
The fatty acid can be released by adding a strong dilute mineral acid(for example, hydrochloric acid), producing a waxy precipitate.
simple equation: RCOONa + HCl ===> RCOOH + NaCl
ionic and more correct:RCOO-(and) + H+(aq) ===> RCOOH(s)
A case of a strong mineral acid displacing a weaker organic carboxylic acid.
The parent ester is a saturated fat found in olive oil, palm oil, and body fats.
This reaction breaks down the fat molecule into one molecule of glycerol (an alcohol triol) and three sodium salts of the long-chain carboxylic acids that were part of the original oil/fat ester.
Sodium stearate is another soap molecule: it's actually a salt of a long-chain fatty acid like stearic acid shown below, released by adding a dilute strong mineral acid (eg hydrochloric acid).
See also 6.9Natural esters - triglyceride fats and oils, margarine and biodiesel production
AVerseifungReaction
TOP OF PAGE and subscript
6.8.4transesterification of esters(Exchange of the acid or alcohol component - transesterification)
From theThe acid-catalyzed esterification reaction is reversible., you can actually change the alcohol or carboxylic acid derivative component in the ester molecule.
(Video) DIBAL-H in Organic Chemistry || Explained by IITian || Jee Mains | Advance | NEET | AIIMSYou gently reflux the ester with another alcohol or carboxylic acid.to carry out the transesterification.
So there are two possibilities, e.g.
(a)Substitution of the alcohol-derived component of the ester
RCOOR' + R"OH
Ester 1 + Alcohol 1
So this effectively changes the alcohol reagent in the esterification.
examples
(YO)Ethylethanolato + Propan-1-ol
+
+
(ii)butilpentanoato + etanol
+
+
The first ester can be called 1-butylpentanoate.
(b)Substitution of the carboxylic acid derivative component of the ester
RCOOR' + R'COOH
ester 1 + carboxylic acid 1
So this effectively exchanges the carboxylic acid reagent in the esterification.
examples
(YO)Propylpentanoate + Buttersäure
(ii)Methylethanolate + Benzoesaure
AThe transesterification reaction is used in the manufacture of margarine and biodiesel.
Ver6.9Natural esters - triglyceride fats and oils, margarine and biodiesel production
TOP OF PAGE and subscript
6.8.5The use of esters
The esters are used inPerfumesyflavorsand most are derived from natural sources, particularly aromatic plants.
Esters are found in the essential oils of plants and in animal pheromones.
solventmay contain esters, for example nail polish remover contains some ethyl ethanoate.
Esters such as ethyl ethanoate and butyl ethanoate are used as high-quality solvents for a variety of materials, including plastics, plasticizers, resins, and paints, and are also used as lubricants and synthetic plasticizers.
Esters are polar, but not very polar, and therefore can dissolve a wide variety of organic compounds.
fragrances and food additives
Perfumes are complex mixtures of esters and ketones, combined to give them a particular volatility and aroma.
Many esters are used as flavor enhancers in fruit drinks and cakes etc etc!
Much of our taste sensation is actually due to the smell of the food we eat, e.g. it smells like esters. When we eat, we smell these ester aromas – think fruity odors/flavors and these odors make food more appetizing.
Flavor molecules, such as esters, are volatile enough to reach olfactory sensory receptors in the nose (food smells good), but be aware that when you have a bad cold and stuffy nose, your appetite seems to decrease and not the food taste as good as the olfactory receptors are blocked!
Below is a selection of esters as skeletal formulas and notes on them, including abbreviated structural formulas, their odor, and natural sources, although they are all now made synthetically, and some of their uses are mentioned both in the text below and in the text below. former.
I have developed two questions based on the diagram and text below to serve as thoseReplyto the questions
Examples of fruity aromas and odors
Most of the molecules shown above (skeletal formulas) and listed below with their abbreviated structural formulas areused in food flavor or perfume industry.
1. CH3KOCH2CH3Ethyl ethanoate found in pears, used in nail polish remover, paint and adhesive formulations
2. CH3CH2CH2CH2KOCH2CH3Ethyl pentanoate, found in apples,
3. CH3KOCH2CH2CH(CH3)23-methylbutyl ethanoate found in pears and bananas,
Additional note on the name: In the alkyl group of the parent alcohol, the carbon attached to the ester bond is considered carbon 1, hence the 3-methyl....
4. CH3CH2CH2KOCH2CH2CH2CH3butyl butanoate, found in pineapples,
CH3CH2KOCH2CH2CH2CH3Butyl propanoate is used in pear candies.
5. HCOOCH2CH3ethyl methanoate, found in raspberries,
6. CH3KOCH2C6H5Benzyl ethanoate, found in pears, raspberries, and jasmine, its aroma is used in perfumes and cosmetics, to flavor foods, and to impart apple and pear flavors to beverages.
7. CH3CH2CH2KOCH2CH2CH2CH2CH3Pentyl butanoate found in apricots, pineapples, strawberries, and pears
8. C6H5CH=CHCOOCH3methylcinnamic acid, found in strawberries,
9. C6H5KOCH2CH3Ethyl benzoate, found in wintergreen and cherry grape oil,
10 CH3CH2CH2KOCH2CH3Ethyl butanoate, found in strawberries, pineapples, and bananas,
11 CH3KOCH2CH2CH2CH3butyl ethanoate, found in apples and honey,
CH3KOCH2CH2CH2CH2CH3Pentyl ethanoate found in banana odor
CH3COO(CH2)7CH3Octyl ethanoate, mainly contributes to the orange odor
(Video) Sodium Borohydride in Organic Chemistry | NaBh4 Details| Explained by IITian | Mains, Advanced| NEET12 CH3CH2CH2CH2CH2KOCH2CH3Ethyl hexanoate, found in pineapples and bananas,
13(CH3)2CHCH2KOCH2CH3ethyl 3-methylbutanoate found in apples,
14 CH3KOCH3Methyl ethanoate, used as a solvent, for example, in adhesive formulations.
Use of esters as plasticizers/plasticizers(note the two spellings, eg for US/UK)
A softener/emollient isa substance added to a material such as polymers to make a plastic that is softer and more flexibleh to increase its plasticity for the final commercial product or to reduce friction during processing and manufacturing of a plastic material.
Plasticizers are needed because the "neat" polymer often does not have the optimal properties desired for a particular application, e.g. 'Pure' PVC is a tough, tough polymer that is too inflexible to be used as insulation for electrical cables. Mix a plasticizer and your cable to a device is flexible!
Plasticized PVC works well for gutters, pipes, and window frames, but you need plasticized PVC for anything that requires flexibility, from cable insulation to plastic raincoats.
The plasticizer allows the polymer chains to move past each other and break the intimate contact, making the polymer less crystalline and smoother.
However, over time, the plasticizer diffuses and evaporates, making the polymer stiffer and less flexible, which can lead to stress cracking.
The esters ofBenzene-1,2-dicarboxylic acid(phthalic acid) shown on the right have been widely used in the past, but hisThe use is restricted for health reasons..
1. Phthalic acid (benzene-1,2-dicarboxylic acid) was reacted with excess alcohol to give the ester 2 .
2. A dialkyl ester of phthalic acid, a phthalate ester.
3. Instead of phthalic acid, phthalic anhydride is more suitable for producing phthalate esters for use as plasticizers.
Examples of phthalate esters used as plasticizers.
4. Diethyl phthalate, dibutyl phthalate is also used.
5. Di-2-ethylhexylphthalate,
6. Dinonyl phthalate, the alkyl part may also be derived from isomeric alcohols of nonyl alcohol (nonan-1-ol, 1-nonanol), p. 7-methyloctan-1-ol
Concerns about the use of phthalate esters as plasticizers.
Animal studies have shown that plasticizers, and particularly phthalate esters, are harmful and can cause birth defects and liver damage. Traces of plasticizers can seep down the sides of the liquid container and be ingested when drinking the liquid and think of little kids sucking/chewing on plastic toys! Despite these concerns, it is considered safe to use phthalate plasticizers in products for medical applications, e.g. tubes and flexible plastic bags.
Safer emollient esters can be made from other dicarboxylic acids, e.g.butanedioic acid(1,4-butanedioic acid, butane-1,4-dioic acid, butane-1,4-dicarboxylic acid, old namesuccinic acid)
7. Succinic acid, HOOCCH2CH2COOH,
8. Diethylsuccinato, CH3CH2OOCCH2CH2KOCH2CH3,
9. Dibutylsuccinato, CH3CH2CH2CH2OOCCH2CH2KOCH2CH2CH2CH3,
biofuelsThey are made ofProduction of fatty acid methyl esters by transesterification.
medical applications
More soluble in fat than water, it is absorbed through the skin and, like aspirin, has an anti-inflammatory effect, reducing pain and swelling.
Aspirin (right) is an ester of acetic acid, but the "alcohol" derived from it is actually a phenol called 2-hydroxybenzoic acid.
Some anesthetics such as benzocaine and procaine are esters.
Benzocaine (left) is the ethyl ester of 4-aminobenzoic acid.
Many anesthetics ("pain relievers") are derived from natural products. Synthetic codeine is made from natural morphine, but it is not an ester. However, the related molecule is natural.Heroin is a double ester.(two CH3COOR groups - I think you recognize the two ester bonds (and also a cyclic ether bond and a tertiary amine group!).
I have written a lot about ituse of esterson another website for GCSE/IGCSE Basic Chemistry
yPart 6.14More about the use of carboxylic acids and derivatives and their presence in nature
See alsoAspirin - another ester!
The 2-methylhydroxybenzoate ester is found in oil of wintergreen and is used as a liniment.
Q1Name the following esters using their basic formulas and draw the abbreviated structural formulas
(ignore the name of 8 at the pre-university level)
REPLY
For basic IGCSE/GCSE review notes, seeEsters, chemistry and applications including fragrances, solventsand more information and links can be found on this page for advanced students of organic chemistry.
Q2. Name the following ester compounds using their abbreviated structural formulas and draw their basic formulas.
2.CH3CH2CH2CH2KOCH2CH33.CH3KOCH2CH2CH(CH3)24.CH3CH2CH2KOCH2CH2CH2CH35.HCOOCH2CH36.CH3KOCH2C6H57.CH3CH2CH2KOCH2CH2CH2CH2CH38.C6H5CH=CHCOOCH3(ignore the name of the eighth at the pre-college level)1.CH3KOCH2CH3
9. C6H5KOCH2CH3
10CH3CH2CH2KOCH2CH3
11CH3KOCH2CH2CH2CH3
12CH3CH2CH2CH2CH2KOCH2CH3
13(CH3)2CHCH2KOCH2CH3
14CH3KOCH3
REPLY