Question

Camphor, a saturated monoketone from the Asian camphor tree, is used as a moth repellent and as a constituent of embalming fluid, among other things. If camphor has \(\mathrm{M}^{+}=152.1201\) by high-resolution mass spectrometry, what is its molecular formula?

Short answer

The molecular formula for camphor is likely C\(_{10}\)H\(_{16}\)O.

Step-by-step solution

Determine Molar Mass

Camphor has a high-resolution mass spectrometric measurement of its molecular ion \( \mathrm{M}^{+} = 152.1201 \). This is the molecular weight we are working with to find the molecular formula.

Identify Possible Elements

Common elements usually present in organic compounds including camphor are carbon (C), hydrogen (H), and oxygen (O). We need to propose a formula using these elements. The average atomic masses are roughly C: 12.01, H: 1.008, O: 16.00.

Estimate Base Formula

Estimate a possible base formula mass. Start by determining a rough count of carbons: \( \frac{152}{12} \approx 12 \). Try using C\(_{10}\), H\(_{16}\), O\(_{1}\) as a likely structure based on typical patterns in similar compounds.

Calculate Exact Formula Mass

Calculate the total mass for C\(_{10}\)H\(_{16}\)O:\- Mass of C\(_{10}\): \(10 \times 12.01 = 120.1\)- Mass of H\(_{16}\): \(16 \times 1.008 = 16.128\)- Mass of O: \(1 \times 16.00 = 16.00\)- Total mass = \(120.1 + 16.128 + 16 = 152.228\)With this approximation, the empirical formula seems close to the measured mass of 152.1201.

Confirm the Formula

The calculated mass (152.228) is reasonably close to the measured mass (152.1201), confirming that Camphor's likely molecular formula is C\(_{10}\)H\(_{16}\)O.

Key concepts

Mass Spectrometry

Mass spectrometry is a powerful tool used to determine the molecular weight and structure of compounds. This method works by ionizing chemical compounds to generate charged molecules or molecule fragments. The key steps involve the following sequential processes:

• Ionization: The compound is ionized, often by an electron beam, causing it to lose an electron and form a molecular ion with a positive charge (e.g., \( \mathrm{M}^+ \)).
• Acceleration: These ions are then accelerated by an electric field.
• Deflection: An electromagnetic field deflects different ions to varying degrees based on their mass-to-charge ratios.
• Detection: The ions are detected, and a spectrum is produced, showing how many ions were detected at each mass-to-charge ratio.

With high-resolution mass spectrometry, the molecular ion peak gives the most accurate molecular weight. For camphor, the precise value \(152.1201\) helps refine the search for its exact molecular formula.

Organic Compound Analysis

Organic compound analysis involves determining the structure and composition of organic compounds. This process is crucial in fields like medicine, materials science, and environmental studies.
A typical analysis might consider the following elements:

• Carbon (C): The backbone of organic molecules, forming chains and rings through covalent bonds.
• Hydrogen (H): Commonly seen bonded with carbon, altering molecular size and properties.
• Oxygen (O): Often present in functional groups like ketones, alcohols, and ethers.

In camphor's example, knowing it is a monoketone (a compound with one ketone group) simplifies the element choice for its analysis. The known presence of C, H, and O suggests a simple molecular formula that aligns with common organic structures.

Molecular Weight Calculation

Calculating molecular weight is an essential part of determining a compound's molecular formula. Here, you sum the atomic masses of all atoms in a molecule. For camphor, a multi-step approach is employed:

• Rough Estimate: Divide the total measured mass by the atomic mass of carbon to approximate the number of carbon atoms (e.g., \( \frac{152}{12} \approx 12 \)). This is adjusted based on common patterns among similar compounds.
• Propose a Formula: Suggest a molecular structure (like \(\text{C}_{10}\text{H}_{16}\text{O}_1\)) and calculate the theoretical mass.
• Refinement: Compare the calculated mass with the precise mass spectrometric value to finalize the formula. For camphor, \(152.228\) is close to the measured \(152.1201\).

This process ensures that the empirical formula reflects the compound's composition accurately, aligning with empirical data gathered through mass spectrometry.