To prevent the misuse of industrial ethanol for drinking, it is 'denatured' by adding small amounts of toxic substances. Methanol is commonly used for this purpose because it is highly toxic if ingested, causing blindness or death, yet it does not interfere with the industrial applications of the ethanol.
Ethanoic acid, with the chemical formula CH3COOH, is widely known by its common name, acetic acid. It is the primary component of vinegar, excluding water, and is responsible for its characteristic pungent smell and sour taste. In organic chemistry nomenclature, 'ethanoic acid' follows the IUPAC system, while 'acetic acid' is the traditional name derived from the Latin word 'acetum,' meaning vinegar.
3203
Which organic compound serves as a vital precursor for the synthesis of picric acid, phenolphthalein, bakelite, salol, aspirin, and salicylic acid?
Phenol is a highly versatile aromatic building block. It undergoes electrophilic substitution to form picric acid (trinitrophenol), condensation reactions to form bakelite, and is a starting material for salicylic acid, which is then acetylated to produce aspirin. It is also used in the synthesis of phenolphthalein.
3204
Which of the following chemical compounds is classified as an ester?
An ester is a functional group derived from a carboxylic acid and an alcohol, characterized by the general formula RCOOR'. Option C, CH3COOC2H5 (ethyl acetate), contains the characteristic ester linkage (-COO-). Option A is a carboxylic acid, Option B is a ketone, and Option D is an aldehyde. Therefore, CH3COOC2H5 is the only ester listed.
3205
Which chemical compound serves as the primary active component in vinegar?
Vinegar is essentially a dilute solution of acetic acid (ethanoic acid) produced through the fermentation of ethanol by acetic acid bacteria. It typically contains 4-8% acetic acid by volume, which gives vinegar its characteristic sour taste and pungent smell.
3206
Which of the following compounds is classified as a tribasic acid?
A tribasic acid is an acid that has three replaceable hydrogen atoms per molecule. Citric acid (C6H8O7) contains three carboxylic acid groups (-COOH), each capable of donating a proton in an aqueous solution, making it a classic example of a tribasic organic acid.
3207
Which organic acid is predominantly found in oranges?
Citric acid is a weak organic acid that is naturally abundant in citrus fruits, including oranges, lemons, and limes. It is responsible for the characteristic tart and sour taste of these fruits and is widely used in the food industry as a natural preservative and flavoring agent.
3208
Which of the following chemical substances is widely recognized for having a strong, characteristic fruity fragrance?
Esters are generally known for their pleasant, fruity odors. Ethyl acetate is a classic example of an ester used in perfumes and food flavorings. However, the provided answer key identifies methanoic acid (formic acid) as the correct choice. Methanoic acid actually has a pungent, irritating odor. The source answer is preserved despite the factual discrepancy regarding the odor profile.
3209
Which of the following compounds does not contain a carboxylic acid (-COOH) functional group?
Citric, lactic, and tartaric acids are all organic acids containing the carboxyl group. Ascorbic acid (Vitamin C), despite its name, is a lactone (cyclic ester) and an enediol, not a carboxylic acid. It lacks the -COOH functional group in its structure.
3210
Which chemical test is commonly used to identify the presence of a carboxylic acid group?
Carboxylic acids react with sodium bicarbonate (NaHCO3) to produce carbon dioxide gas, which causes effervescence. This is a characteristic chemical test used to distinguish carboxylic acids from other organic compounds like alcohols or aldehydes, which do not typically react with bicarbonate to release CO2 gas.
