Question

Propose a structural formula for compound \(\mathrm{J}\), molecular formula \(\mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}\), consistent with the following \({ }^{1} \mathrm{H}\)-NMR spectrum.

Short answer

Question: Based on the given step by step solution, describe the process of determining the structural formula of compound J with a molecular formula of C₃H₆O from its ¹H-NMR spectrum data. Answer: To determine the structural formula of compound J from its ¹H-NMR spectrum data, follow these steps: 1. Identify the types of hydrogen environments by observing the number of different peaks and their chemical shift values. 2. Determine the integration of the peaks to estimate the ratio of protons in each environment. 3. Analyze the multiplicity of the peaks and use the n+1 rule to determine J-coupling between protons. 4. Identify potential functional groups based on the shift values and molecular formula C₃H₆O. 5. Propose a structural formula consistent with the molecular formula and ¹H-NMR spectrum data, including proton types, peak integration, and peak multiplicity.

Step-by-step solution

Identify the types of hydrogen environments in the \({}^{1}\mathrm{H}-\mathrm{NMR}\) spectrum.

Look at the \({}^{1}\mathrm{H}-\mathrm{NMR}\) spectrum and check the number of different peaks as well as the peaks' chemical shift values. Each peak represents a hydrogen environment with protons in a similar chemical environment.

Determine the integration of the peaks.

Utilize the integration value present in the \({}^{1}\mathrm{H}-\mathrm{NMR}\) spectrum to estimate the relative ratio of protons in each environment. These values would give the number of protons in a chemical environment with respect to each other.

Analyze the Multiplicity of the Peaks

Look for the splitting patterns or multiplicity of the peaks (doublet, triplet, etc.), as they provide insight into the J-coupling present between protons in the molecule. For instance, the n+1 rule can be applied: if a hydrogen has n neighboring protons, expect a splitting pattern into n+1 peaks.

Identify functional groups

Analyze the shift values from \({}^{1}\mathrm{H}-\mathrm{NMR}\) and use the molecular formula \(\mathrm{C}_{3}\mathrm{H}_{6}\mathrm{O}\) to identify any potential functional groups. For example, an aldehyde proton generally has a shift around 9-10 ppm, alcohol protons are typically 1-4.5 ppm, and proton signals from alkyl groups are 0.9-2 ppm.

Propose a structural formula

Use the information gathered from Steps 1-4 to deduce the structural formula for compound J. Compare different structural possibilities to ensure consistency with the molecular formula and \({}^{1}\mathrm{H}-\mathrm{NMR}\) spectrum data, such as the number of each type of proton, the integration of each peak, and peak multiplicity.

Key concepts

Structural Formula Determination

Determining the structural formula of a compound using 1H NMR Spectroscopy involves a systematic approach of analyzing the provided spectrum data. When faced with a molecular formula like \( \mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O} \) and an NMR spectrum, the first step is to break down the molecule into various hydrogen environments.

Essentially, each distinct peak in the NMR spectrum corresponds to hydrogens in a unique electronic environment. These environments are influenced by adjacent atoms and functional groups. Subsequently, we can start piecing together the structure by considering how these environments might connect in a logical manner, adhering to the rules of organic chemistry.

For a molecule such as compound J, one has to consider all possible structures that fit the formula \( \mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O} \) and then use the NMR data to eliminate unlikely options until the correct structure is identified. Each step, from identifying hydrogen environments to analyzing the integration of peaks and their multiplicity, leads us closer to visualizing the compound’s backbone and any functional groups present.

Peak Integration in NMR

Peak integration in 1H NMR Spectroscopy serves as a quantitative tool to determine the number of protons that contribute to a particular signal. In essence, each peak in the NMR spectrum area is proportional to the number of hydrogen atoms in that environment.

An integrated NMR spectrum will often include numerical values above or beneath the peaks that correlate to the relative number of protons. These values are essential in construction of the structural formula, as they guide you in piecing together how many hydrogen atoms are in each chemical environment.

With compound J, the integration values provide critical clues to deduce how the C₃H₆O molecule is assembled. For instance, if one peak integrates to a value of 3, this indicates that there are three hydrogens in that particular magnetic environment, which can signify the presence of a methyl group or a propane-like sequence, depending on other spectral data.

NMR Peak Multiplicity

Multiplicity in 1H NMR Spectroscopy refers to the splitting patterns observed in the spectrum peaks. This pattern reveals the 'neighborhood' of a given hydrogen, meaning the number of adjacent hydrogens that influence its magnetic environment through spin-spin coupling.

The n+1 rule is a handy axiom in analyzing multiplicity. It predicts that if a hydrogen atom has n neighboring hydrogens, you can expect a splitting into n+1 peaks. For example, a triplet indicates two adjacent protons (\(2+1=3\) peaks), while a quartet suggests three neighbors (\(3+1=4\) peaks).

In the case of compound J, scrutinizing the multiplicity of each peak aids in understanding the connectivity between different hydrogen-containing groups. This information is crucial because it helps to clarify which hydrogens may be adjacent to one another and, thus, indicate the skeleton of the molecule in question.

Functional Group Identification in NMR

Identification of functional groups using 1H NMR Spectroscopy is largely determined by the chemical shift values observed in the spectrum. Chemical shifts tell us about the electron density around hydrogens, and therefore indicate what type of functional groups might be present.

Hydrogens attached to oxygen, as in alcohols or ethers, typically resonate at higher ppm values due to the electronegative effect of oxygen. This helps to distinguish, for example, an alcohol group from an alkyl chain. In the scenario of compound J with the formula \( \mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O} \), identifying the correct functional group is fundamental.

By considering the specific shift ranges – such as upfield ranges for alkyl hydrogens and downfield for more electronegative groups – one can begin to match the molecular structure to the spectral data. It's a process of elimination and hypothesis testing, where chemical shift values significantly narrow down the structural possibilities.