Ultimate Organic Chemistry Quiz

Acetone can be tested by iodoform because when acetone reacts with iodine and sodium hydroxide, it forms a yellow precipitate of iodoform. This reaction is a characteristic test for the presence of acetone. Therefore, the statement "Acetone can be tested by iodoform" is true.

Acetone can be tested by the iodoform test because it contains a methyl ketone group. The iodoform test is used to detect the presence of methyl ketones, such as acetone, by reacting them with iodine and a base. This reaction produces a yellow precipitate of iodoform, which confirms the presence of acetone. Therefore, the given statement is true.

The Vigreux column is a type of fractionating column that is designed to improve the separation of compounds with a small boiling point difference. It consists of a series of indentations or "baffles" along the length of the column, which increases the surface area available for vaporization and condensation. This increased surface area allows for more efficient separation of compounds with a boiling point difference of 30-40°C. Therefore, the statement that the Vigreux column allows reasonable separation of compounds with a boiling point difference of 30-40°C is true.

Chloral hydrate is a compound that contains a hydroxyl group (-OH) attached to the chloral molecule. This hydroxyl group can form two hydrogen bonds with other molecules or functional groups. On the other hand, chloral does not have a hydroxyl group and therefore cannot form hydrogen bonds. Hence, the statement that chloral hydrate can form two hydrogen bonds while chloral cannot is true.

When a more volatile component is added, the total vapor pressure of the liquid mixture increases, so the temperature required for the vapor pressure to equal external pressure decreases. This leads to a lower boiling point compared with the original less volatile liquid.

Electron-withdrawing groups at the para position increase the acidity of phenol by stabilizing the conjugate base (phenoxide), but they decrease its nucleophilicity by reducing electron density. So the statement saying they decrease both acidity and nucleophilicity is false.

The classic product of such a reaction (with anilide systems) is typically named 2-hydroxyimino-N-phenyl acetanilide (which appears as option C if that’s what you meant). 

Although their boiling points differ significantly, separating them efficiently by fractional distillation is not ideal in practice due to high boiling temperatures and possible decomposition. Hence, other methods (e.g. steam distillation, recrystallization) are preferred.

The definition of boiling point (for both pure liquids and solutions) is the temperature at which vapor pressure equals external pressure. What changes for a solution is the value of the boiling point (usually higher than the pure solvent with a non-volatile solute), but the definition stays the same.

Vacuum distillation is used to separate heat-sensitive or thermolabile liquid compounds at reduced pressure (below atmospheric pressure), not at 1atm. By lowering the pressure, the boiling point of the compounds decreases, allowing for separation without decomposition. Therefore, the given statement is false.

Steam distillation is a technique used to separate volatile compounds from non-volatile substances. In this process, steam is passed through the mixture, causing the volatile compounds to vaporize. The vapor is then condensed and collected, resulting in the separation of the desired compound. The splash head is a crucial component in steam distillation as it helps in controlling the flow of steam and preventing any splashing or loss of the mixture. Therefore, the splash head is specifically designed for steam distillation, making it the correct answer.

In practice, chloral hydrate (CCl₃CH(OH)₂) is more stable and easier to handle than chloral (CCl₃CHO) and is commonly used in lab syntheses (including the classical preparation of “isonitroso” derivatives). So the statement is closer to True in standard instructional chemistry.

Phenols can be oxidized to quinones under mild conditions. Very strong oxidizing conditions may further break down the aromatic ring to carboxylic acids or CO₂. The original statement is oversimplified and not generally valid.

Cooling in an ice bath during the synthesis of p-iodobenzoic acid from p-aminobenzoic acid is crucial to control the highly exothermic diazotization reaction. Maintaining a low temperature (0-5°C) stabilizes the intermediate diazonium salt, preventing its decomposition and the formation of unwanted by-products. This ensures a successful Sandmeyer reaction, where the diazonium group is replaced with an iodine atom, yielding p-iodobenzoic acid with minimal side reactions.