Question

The following is the mass spectrum of compound \(\mathrm{C}, \mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O}\). Compound \(\mathrm{C}\) is infinitely soluble in water, undergoes reaction with sodium metal with the evolution of a gas, and undergoes reaction with thionyl chloride to give a water-insoluble chloroalkane. Propose a structural formula for compound \(C\) and write equations for each of its reactions.

Short answer

Answer: The structure of compound C is isopropanol (CH3CHOHCH3). The balanced chemical equations for its reactions with sodium metal and thionyl chloride are: - Reaction with sodium: 2 CH3CHOHCH3 + 2 Na → 2 CH3CHONaCH3 + H2↑ - Reaction with thionyl chloride: CH3CHOHCH3 + SOCl2 → CH3CHClCH3 + SO2↑ + HCl↑

Step-by-step solution

Analyze the given information

We know that compound C has the molecular formula C3H8O, and it exhibits the following properties: - Infinitely soluble in water. - Reacts with sodium metal to produce a gas. - Reacts with thionyl chloride to form a water-insoluble chloroalkane.

Determine possible structures

Since compound C has the molecular formula C3H8O, there are two possible structures for this compound: 1. Propanol (CH3CH2CH2OH): A primary alcohol with a hydroxyl group attached to a carbon at one end of the molecule. 2. Isopropanol (CH3CHOHCH3): A secondary alcohol with a hydroxyl group attached to a carbon in the middle of the molecule.

Propose the most likely structure

Let us analyze the properties of each possible structure as they relate to the given information: 1. Propanol: Soluble in water due to the hydroxyl group, but it is less soluble than a secondary alcohol. It reacts with sodium to produce hydrogen gas, and with thionyl chloride to form propyl chloride. 2. Isopropanol: Infinitely soluble in water due to the more polar nature of the secondary alcohol. It reacts with sodium to produce hydrogen gas, and with thionyl chloride to form isopropyl chloride (which is less soluble in water than propyl chloride, a primary alkyl halide). Based on the fact that compound C is infinitely soluble in water, isopropanol is the most likely structure.

Write balanced chemical equations

Now, we will write balanced chemical equations for the reactions of isopropanol with sodium and thionyl chloride: - Reaction with sodium: \[ 2\, \mathrm{CH_{3}CHOHCH_{3}} + 2\, \mathrm{Na} \rightarrow 2\, \mathrm{CH_{3}CHONaCH_{3}} + \mathrm{H_{2}} \uparrow \] - Reaction with thionyl chloride: \[ \mathrm{CH_{3}CHOHCH_{3}} + \mathrm{SOCl_{2}} \rightarrow \mathrm{CH_{3}CHClCH_{3}} + \mathrm{SO_{2}} \uparrow + \mathrm{HCl} \uparrow \] In conclusion, compound C is isopropanol, and the balanced chemical equations for its reactions with sodium metal and thionyl chloride are given above.

Key concepts

Mass Spectrum Analysis

Mass spectrum analysis is a powerful tool in organic chemistry for determining the structure of a compound. By analyzing the fragmentation pattern of a molecule when it is ionized, we can infer the mass-to-charge ratio of the fragments, which gives us clues about the molecular structure. In the context of the mass spectrum of the compound C3H8O, the analysis could reveal the presence of characteristic peaks corresponding to the molecular ion and its fragments.

For a student attempting to decode the mass spectrum, it is essential to look for patterns such as the M+ peak, which represents the molecular ion, and to compare the fragmentation pattern to known structures to deduce the most plausible structure. In complex cases, the process may involve looking at isotopic distribution and considering the stability of resultant ions. The key is to correlate the mass spectral data with the chemical properties and reactions of the compound to arrive at a reliable structure.

Solubility in Organic Compounds

Solubility in organic compounds is heavily influenced by molecular structure, particularly by the presence of polar functional groups like hydroxyl (-OH) that can engage in hydrogen bonding with water molecules. In the case of compound C (C3H8O), which is described as 'infinitely soluble in water', this implies that the compound has strong polarity or a functional group capable of extensive hydrogen bonding.

Comparing propanol and isopropanol, the infinite solubility suggests the structure is more likely to be isopropanol due to the secondary alcohol's ability to form stronger interactions with water. When explaining solubility to students, emphasize the relevance of polarity, the functional groups present, and their arrangement in the molecule, as these factors contribute significantly to the solubility in polar solvents like water.

Alkyl Halide Formation

Alkyl halide formation is a common reaction in organic chemistry, and knowing how different alcohols react to form these compounds is essential. Thionyl chloride (SOCl2) is often employed to convert alcohols into alkyl chlorides, a process which proceeds through the formation of a chlorosulfite intermediate and the subsequent elimination of sulfur dioxide (SO2) and hydrogen chloride (HCl) gases.

The reaction of isopropanol with thionyl chloride, as detailed in the exercise, involves the substitution of the hydroxyl (-OH) group by a chlorine atom to form isopropyl chloride. This transformation underscores the nucleophilic substitution mechanism, which is typical of alcohols reacting with thionyl chloride. For a better understanding, students should focus on the leaving group ability, the nature of the alcohol (primary, secondary, tertiary), and the mechanism that determines the reactivity and the outcome of such reactions.