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Synthetic Polymers, Carbohydrates, Amino Acids, and Proteins

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Question 1Question →

During the industrial synthesis of a synthetic fiber, hexanedioic acid reacts with hexane-1,6-diamine with the elimination of water molecules to form amide linkages. Which polymer is formed from this process?

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Answer: Nylon-6,6

Answer

Nylon-6,6 is the polyamide formed by the condensation polymerization of hexanedioic acid and hexane-1,6-diamine.
The reaction between a dicarboxylic acid containing 6 carbon atoms (hexanedioic acid) and a diamine containing 6 carbon atoms (hexane-1,6-diamine) yields a synthetic polyamide known as Nylon-6,6 via condensation polymerization with the elimination of water.

Step-by-Step Solution

1
Identify the functional groups of the monomers provided in the prompt.
Hexanedioic acid contains dicarboxylic acid groups (−COOH-COOH) and hexane-1,6-diamine contains diamine groups (−NH2-NH_2).
The reaction between carboxylic acid and amine functional groups forms peptide/amide bonds (−CONH−-CONH-).
2
Determine the type of polymerization and the resulting macromolecule class.
The reaction involves the loss of water molecules, which defines condensation polymerization forming a polyamide.
Condensation polymerization links bifunctional monomers together with the elimination of small molecules such as H2OH_2O.
3
Match the specific monomers to the corresponding polymer name.
Hexanedioic acid (6 carbon atoms) and hexane-1,6-diamine (6 carbon atoms) produce Nylon-6,6.
The numbers '6,6' in Nylon-6,6 indicate that both the diamine and dicarboxylic acid monomers contain 6 carbon atoms each.

Key Concept

Condensation Polymerization and Synthesis of Polyamides (Nylon-6,6)
Question 2Question →

An unknown disaccharide XX with the molecular formula C12H22O11\text{C}_{12}\text{H}_{22}\text{O}_{11} does not reduce Fehling's solution. Upon acid-catalyzed hydrolysis, XX yields an equimolar mixture of two isomeric hexoses, YY and ZZ. Compound YY rapidly produces a deep red color when heated with Seliwanoff's reagent, whereas compound ZZ is oxidized by bromine water to form a monocarboxylic acid. Which of the following correctly identifies disaccharide XX and explains why it fails to react with Fehling's solution prior to hydrolysis?

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Answer: Sucrose; because the glycosidic linkage involves the anomeric carbons of both glucose and fructose, eliminating free hemiacetal/hemiketal groups.

Answer

Sucrose; because the glycosidic linkage involves the anomeric carbons of both glucose and fructose, eliminating free hemiacetal/hemiketal groups.
Seliwanoff's test specifically identifies ketohexoses such as fructose through rapid dehydration to hydroxymethylfurfural and reaction with resorcinol. Bromine water selectively oxidizes aldoses like glucose to aldonic acids without oxidizing ketoses. A disaccharide yielding glucose and fructose upon hydrolysis is sucrose. Sucrose is a non-reducing sugar because its glycosidic bond connects C-1 of glucose and C-2 of fructose, locking both anomeric carbon atoms and preventing ring opening to form reactive carbonyl groups.

Step-by-Step Solution

1
Analyze the chemical test results of the hydrolysis products YY and ZZ.
Compound YY gives a positive Seliwanoff's test (rapid red color), which is characteristic of a ketose (fructose). Compound ZZ is oxidized by bromine water (a mild oxidizing agent), which selectively oxidizes aldoses (glucose) to aldonic acids.
Seliwanoff's reagent differentiates ketoses from aldoses, while bromine water differentiates aldoses from ketoses.
2
Identify the disaccharide XX based on its hydrolysis products.
Disaccharide XX hydrolyzes into glucose and fructose, identifying XX as sucrose.
Sucrose (C12H22O11\text{C}_{12}\text{H}_{22}\text{O}_{11}) is composed of one glucose unit and one fructose unit.
3
Determine the structural basis for the non-reducing nature of sucrose.
In sucrose, the glycosidic bond connects C-1\text{C-1} (α\alpha-anomeric carbon of glucose) to C-2\text{C-2} (β\beta-anomeric carbon of fructose).
Because both potential reducing centers (anomeric carbons) are locked in the glycosidic bond, sucrose lacks a free hemiacetal or hemiketal group, rendering it a non-reducing sugar that does not reduce Fehling's reagent.

Key Concept

Glycosidic bond linkages and reducing vs. non-reducing carbohydrate behavior
Question 3Question →

Four organic substances—starch, nylon-6,6, polyethene, and natural rubber—were analyzed to compare their chemical structures, reaction behaviors, and environmental properties. Which of the following statements provides a correct scientific comparison among these materials?

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Answer: Starch consists of monomeric glucose units joined by glycosidic linkages that undergo acid hydrolysis, whereas nylon-6,6 contains recurring amide linkages formed via condensation polymerization.

Answer

Starch consists of monomeric glucose units joined by glycosidic linkages that undergo acid hydrolysis, whereas nylon-6,6 contains recurring amide linkages formed via condensation polymerization.
Starch is a carbohydrate (polysaccharide) composed of glucose units connected by glycosidic bonds that can be broken down by acid hydrolysis. Nylon-6,6 is a synthetic condensation polymer (polyamide) made from a dicarboxylic acid and a diamine, containing amide linkages.

Step-by-Step Solution

1
Analyze the structural classification and linkages of starch and nylon-6,6.
Starch is a naturally occurring polysaccharide composed of glucose monomer units linked via α\alpha-glycosidic bonds. Nylon-6,6 is a synthetic polyamide composed of hexanedioic acid and hexane-1,6-diamine monomers joined by amide (−CO−NH−-\text{CO}-\text{NH}-) linkages with the elimination of water.
Identifying monomer units and linkage types distinguishes condensation polymers and carbohydrates.
2
Evaluate the biodegradability of synthetic addition polymers like polyethene versus natural polymers like starch.
Starch is readily degraded by enzymatic action and micro-organisms. Polyethene is a synthetic addition polymer containing strong C−C\text{C}-\text{C} single bonds that resist microbial enzymatic attack, rendering it non-biodegradable.
Synthetic addition polymers lack functional linkages susceptible to hydrolysis.
3
Assess the chemical action of concentrated H2SO4\text{H}_2\text{SO}_4 on carbohydrates.
Concentrated H2SO4\text{H}_2\text{SO}_4 acts as a dehydrating agent, removing water elements from starch according to (C6H10O5)n→conc. H2SO46nC+5nH2O(\text{C}_6\text{H}_{10}\text{O}_5)_n \xrightarrow{\text{conc. H}_2\text{SO}_4} 6n\text{C} + 5n\text{H}_2\text{O}, turning the sample black.
This is a dehydration reaction, not an acid-base neutralization.
4
Analyze the chemical test reagents for unsaturation in rubber versus terminal alkynes.
Bromine water or acidified KMnO4\text{KMnO}_4 is used to test for unsaturation in alkenes and dienes like natural rubber. Ammoniacal silver nitrate selectively reacts with terminal alkynes to give a silver acetylide precipitate.
Different unsaturated functional groups require specific chemical reagents for qualitative identification.

Key Concept

Classification of polymers and biomolecules by linkage type (glycosidic vs amide), reaction mode (addition vs condensation), and chemical reactivity.
Estimated Time:2m 0s
Question 4Question →

Match each synthetic polymer or biomolecule listed in Column A with its corresponding chemical linkage and structural classification in Column B.

Click a left item, then click its matching right item

Items

Nylon-6,6
Terylene (Dacron)
Starch
Protein

Matches

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Answer

Nylon-6,6 pairs with polyamide linkage formed from hexanedioic acid and hexane-1,6-diamine; Terylene pairs with polyester linkage formed from benzene-1,4-dicarboxylic acid and ethane-1,2-diol; Starch pairs with glycosidic linkage formed from α\alpha-D-glucose monomers; Protein pairs with peptide linkage formed from α\alpha-amino acid monomers.
Each polymer is correctly matched to its functional linkage and monomer constituents: Nylon-6,6 is a polyamide formed from hexanedioic acid and hexane-1,6-diamine; Terylene is a polyester formed from benzene-1,4-dicarboxylic acid and ethane-1,2-diol; Starch is a polysaccharide held together by glycosidic linkages between glucose units; Protein is a natural polymer made of amino acids linked by peptide bonds.

Step-by-Step Solution

1
Identify the monomer composition and functional groups of Nylon-6,6
Nylon-6,6 contains amide linkages formed between carboxylic acid (−COOH-\text{COOH}) groups of hexanedioic acid and amino (−NH2-\text{NH}_2) groups of hexane-1,6-diamine.
Synthetic polyamides require a di-acid and a di-amine reactant.
2
Identify the monomer composition and functional groups of Terylene
Terylene contains ester linkages (−COO−-\text{COO}-) formed between benzene-1,4-dicarboxylic acid and ethane-1,2-diol.
Polyesters are produced by reacting a dicarboxylic acid with a dihydric alcohol (diol).
3
Determine the structural linkages present in Starch
Starch is a polysaccharide composed of α\alpha-D-glucose monomers linked via condensation through glycosidic bonds.
Carbohydrates form ether-like condensation links known as glycosidic linkages.
4
Determine the structural linkages present in Proteins
Proteins are natural polymers made of α\alpha-amino acids joined together by peptide linkages (−CO−NH−-\text{CO}-\text{NH}-).
The reaction between the carboxyl group of one amino acid and the amino group of another forms a peptide bond.

Key Concept

Structural linkages and monomeric constituents of synthetic condensation polymers and natural biomolecules
Estimated Time:1m 30s
Synthetic Polymers, Carbohydrates, Amino Acids, and Proteins Practice Questions — JAMB UTME | Examkin