Carboxylic acidsare versatile organic compounds, They have excellent physical andchemicalproperties.The carboxylic acidchemical structure containsa carbonylfunctional group and a hydroxyl group. It interacts easily with polar compounds andcontributes to many important chemical reactions.The carboxylic acid isthe mostimportant functional group that present C O.THEORYCarboxylic acids have tendency to donate protons and they act as acids. It is thisproperty which is helpful in the identification of a - COOH group. Qualitative tests thatcan be performed to identify carboxylic functional group include litmus test, sodiumbicarbonate test or sodium hydrogen carbonate test, ester test and Fluorescein test.Litmus test.The carboxylic acid turns blue litmus paper red. Because the hydroxyl group present in -COOH is far acidic than in alcohol. The chemical reaction is given below.R-COOH +H2 O R- COO-+ H3O+If the colour of the blue litmus paper changes to red then carboxylic group is present.Phenol produce positive results with this test.Sodium bicarbonate test:When carboxylic acid reacts with sodium bicarbonate solution, carbon dioxide isevolved with a brisk effervescence along with the formation of sodium acetate.The chemical reaction is given below.RCOOH + NaHCOs - RCOONa + H20 + CO21 (brisk effervescence)This test is used to distinguish between carboxylic acid from phenol. Phenol does notgive positive results with this test.3.Ester testCarboxylic acid reacts with alcohol in the presence of concentrated sulfuric acid forms apleasant-smelling ester. This reaction is known as esterification. Formation of a sweet-smelling compound indicates the presence of carboxylic group in the given organiccompound.Reaction: RCOOH + R-OH + H2SO4 RO OO-R (ester) + H2O4.Fluorescein testThis test is carried on dicarboxylic acid. Dicarboxylic acid on heating gives acidanhydrideWhen this anhydrideis treated with resorcinol inthe presence ofconcentrated sulfuric acid, a fluoresscent dye is formed and so this reaction is calledfluorescein test. This test should be performed only if the oompound gives positiveresults in litmus test and sodium bicartte test.Reagents and apparatus needed to perforn qualitative test on carboxylic acids andphenols are blue litmus paper, sodium bicarbonate (or) sodium hydrogen carbonate,ethyl alcohol, concentrated sulfuric acid, resorcinol, acid anhydride, test tubes, test tubeholders, beaker, glass rod and stirrer.CASE STUDYThe Quality Control and Assurance Department of Ghana Standard Authority (GSA)identified two organic solvents in their storeroom with their labels torn but suspected tobe benzoic acid and phenol. To ascertain if indeed the organic solvents are benzoicacid and phenol, qualitative test was carried out on the organic solvents. For easyidentification, the solvents were labeled as I and J. The protocols used for the qualitativeCarefully study Table 4 andanalysis and the observations made are shown in Table 4.fill in the empty spaces provided. Answer the follow- up questions.1.Itemise one industrial application of benzoic acid and phenol. Table 4: Protocols for carrying out qualitative test on carboxylic acid and phenolS/N ProtocolObservationSample I was dropped on a blue litmusInferencepaper. Sample J was also dropped on aand J were suspected todifferent blue litmus paperbe benzoic acid and phenol3 ml of sample I was put into a dry test tubeand2 ml of ethyl alcohol was added,I was suspected to bephenolfollowed by 2 mi of concentrated H;SO. Themixture was heated in a water bath.3 ml of sample J was put into a test tube and1 ml of saturated NaHCO, was added. TheBrisk effervescence of a gas was evolvedmixture was shaken thoroughly using arubber cork4.No visible reaction occurredI wassuspected to bephenol5.Sweet smelling substance was sensedsuspected to bewasbenzoic acidwasconfirmed toColour of mixture changed to green6.phenolwas confirmedtobebenzoic acid.7.3 ml of sample J was put into a test tube and100 mg of resorcinol and 0.5 ml of H2SO4were added. The mixture was heated gentlyon a Bunsen burner. The mixture was thenpoured into a beaker containing dilute NaOHsolution.2. Propose a balanced chemical equation for item 33. Propose a balanced chemical equation for item 54. State two precautionary measures adopted to ensure that protocol 3 in Table 4 was carried out successfully5. With the aid of a diagram describe an experiment that could be done to confirm that the gas evolved in item 3 iscarbon (iv) oxide

Case study: The solutions present in the laboratory are labeled as I and J. The compounds are…

Table 4: Protocols for carrying out qualitative test on carboxylic acid and phenol S/N Protocol 1. Observation Inference 1 and J were suspected to Sample I was dropped on a blue itmus paper. Sample J was also dropped on a different blue litmus paper be benzoic acid and phenol 2 3 ml of sample I was put into a dry test tube 1 was suspected to be and 2 ml of ethyl alcohol was added, followed by 2 ml of concentrated H;SO. The phenol mixture was heated in a water bath. 3 mi of sample J was put into a test tube and Brisk effervescence of a gas was evolved 1 ml of saturated NaHCO, was added. The 3. mixture was shaken thoroughly using a rubber cork. 4. No visible reaction occurred 1. Suspected to be was phenol 5. Sweet smelling substance was sensed suspected to be was benzoic acid 1. was confirmed to be Colour of mixture changed to green 6. phenol be was confirmed to benzoic acid 7. 3 ml of sample J was put into a test tube and 100 mg of resorcinol and 0.5 ml of H2SO. were added. The mixture was heated gently on a Bunsen burner. The mixture was then poured into a beaker containing dilute NaOH solution. 2. Propose a balanced chemical equation for item 3 3. Propose a balanced chemical equation for item 5

Table 4: Protocols for carrying out qualitative test on carboxylic acid and phenol S/N Protocol 1. Observation Inference 1 and J were suspected to Sample I was dropped on a blue itmus paper. Sample J was also dropped on a different blue litmus paper be benzoic acid and phenol 2 3 ml of sample I was put into a dry test tube 1 was suspected to be and 2 ml of ethyl alcohol was added, followed by 2 ml of concentrated H;SO. The phenol mixture was heated in a water bath. 3 mi of sample J was put into a test tube and Brisk effervescence of a gas was evolved 1 ml of saturated NaHCO, was added. The 3. mixture was shaken thoroughly using a rubber cork. 4. No visible reaction occurred 1. Suspected to be was phenol 5. Sweet smelling substance was sensed suspected to be was benzoic acid 1. was confirmed to be Colour of mixture changed to green 6. phenol be was confirmed to benzoic acid 7. 3 ml of sample J was put into a test tube and 100 mg of resorcinol and 0.5 ml of H2SO. were added. The mixture was heated gently on a Bunsen burner. The mixture was then poured into a beaker containing dilute NaOH solution. 2. Propose a balanced chemical equation for item 3 3. Propose a balanced chemical equation for item 5

Chemistry

10th Edition

ISBN:9781305957404

Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Chapter1: Chemical Foundations

Section: Chapter Questions

Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...

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