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Difficulty: HardChemistry in Daily Life and Industrial Applications

Regarding the chemical characteristics and functions of industrial and household chemical agents, which of the following statements are correct?

  1. Aspartame decomposes at elevated cooking temperatures, restricting its utility as an artificial sweetener primarily to cold foods and unheated beverages.Answer
  2. Vulcanization of natural rubber involves heating crude polyisoprene with elemental sulfur to form inter-chain disulfide cross-links, enhancing mechanical strength and thermal stability.Answer
  3. Anionic detergents feature long hydrophobic hydrocarbon chains connected to hydrophilic sulfonate or sulfate groups where the surface-active portion carries a net negative charge.Answer
  4. D
    Butylated Hydroxytoluene (BHT) functions as a synthetic food preservative by generating reactive free radicals that promote the rapid oxidative breakdown of fats and oils.

Answer

The statements asserting that aspartame decomposes at elevated cooking temperatures, vulcanization improves natural rubber through sulfur cross-linking, and anionic detergents feature negatively charged surface-active hydrophobic sulfonate groups are correct. The statement regarding Butylated Hydroxytoluene (BHT) is incorrect because BHT acts as a free-radical scavenger to prevent fat oxidation rather than promoting radical formation.
The correct statements accurately state the thermal instability of aspartame, the cross-linking function of sulfur in rubber vulcanization, and the ionic charge structure of anionic synthetic detergents. Aspartame decomposes when heated due to peptide hydrolysis; sulfur bridges anchor polyisoprene chains during vulcanization; and anionic detergents derive their surfactant action from negatively charged polar heads.

Step-by-Step Solution

1
Evaluate the chemical stability of aspartame under heat.
Aspartame degrades at elevated cooking temperatures due to peptide bond breakdown, making it suitable only for cold foods and beverages.
Peptides undergo thermal decomposition and hydrolysis, leading to loss of sweetness.
2
Analyze the chemical mechanism and structural changes in rubber vulcanization.
Heating cis-1,4-polyisoprene with sulfur introduces sulfur bridge cross-links between polymer chains, upgrading elasticity, tensile strength, and thermal resilience.
Cross-linking restricts chain sliding while allowing reversible elastic recovery.
3
Assess the structural classification of synthetic anionic detergents.
Anionic detergents dissociate in aqueous solutions to yield surfactant anions with long-chain hydrophobic groups attached to sulfate or sulfonate anions.
The active detergent ion responsible for micelle formation and cleansing carries a negative charge.
4
Examine the preservative mechanism of Butylated Hydroxytoluene (BHT).
BHT functions as a radical scavenger (antioxidant) that inhibits lipid peroxidation rather than promoting free-radical oxidative decay.
Hindered phenols donate hydrogen to peroxy radicals, forming stable non-radical products.

Key Concept

Chemical principles governing artificial sweeteners, synthetic detergents, polymer vulcanization, and food antioxidants.
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Topics

Chemistry in Daily Life and Industrial Applications

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