Ethers are not easily differentiated by their infrared spectra, but they tend to form predictable fragments in the mass spectrum. The following compounds give similar but distinctive mass spectra.
Both compounds give prominent peaks at m/z 116, 73, 57, and 43. But one compound gives a distinctive strong peak at 87, and the other compound gives a strong peak at 101. Determine which compound gives the peak at 87 and which one gives the peak at 101. Propose fragmentations to account for the ions at m/z 116, 101, 87, and 73.

Verified step by step guidance

1. Identify the molecular structures of the two ether compounds: the first compound is diethyl ether (CH3CH2OCH2CH3) and the second compound is methyl butyl ether (CH3OCH2CH2CH2CH3).
2. Determine the molecular ion peaks (M+) for both compounds: diethyl ether has a molecular weight of 74 g/mol, and methyl butyl ether has a molecular weight of 88 g/mol.
3. Analyze the mass spectrum peaks: both compounds give prominent peaks at m/z 116, 73, 57, and 43. The distinctive peaks are at m/z 87 for one compound and m/z 101 for the other.
4. Propose fragmentations: for diethyl ether, the peak at m/z 87 can be attributed to the loss of a CH3 group (M+ - 15), and for methyl butyl ether, the peak at m/z 101 can be attributed to the loss of a CH3 group (M+ - 15).
5. Account for the ions at m/z 116, 101, 87, and 73: m/z 116 is likely a common fragment for both compounds, m/z 101 is specific to methyl butyl ether, m/z 87 is specific to diethyl ether, and m/z 73 can be a common fragment resulting from the loss of an ethyl group (C2H5).

Key Concepts

Mass Spectrometry Fragmentation

Mass spectrometry fragmentation involves the breaking of chemical bonds in a molecule to produce smaller ions, which can be detected and analyzed. The pattern of these fragments provides insight into the structure of the original compound. Each fragment corresponds to a specific mass-to-charge ratio (m/z), allowing chemists to deduce the molecular structure based on the observed peaks in the mass spectrum.

Ethers and Their Structure

Ethers are organic compounds characterized by an oxygen atom connected to two alkyl or aryl groups. Their general structure is R-O-R', where R and R' can be the same or different. The unique structural features of ethers influence their fragmentation patterns in mass spectrometry, leading to distinctive peaks that can help differentiate between similar compounds.

Interpreting Mass Spectra Peaks

Interpreting mass spectra peaks involves analyzing the m/z values to identify the corresponding fragments and their origins. Each peak represents a specific ion formed during fragmentation, and the intensity of the peaks indicates the relative abundance of those ions. By comparing the peaks at m/z 116, 101, 87, and 73, one can deduce which compound produces which peak and propose possible fragmentation pathways.