(a)
Interpretation:
The peaks of
Concept introduction:
In mass spectrometry, an electron is lost to form a molecular ion. Two types of fragmentation occur. A stable molecular ion decomposes slowly and a peak with large relative abundance is detected in the mass spectrometer. If the molecular ion is unstable, it decomposes into several ions.
(b)
Interpretation:
The stable neutral molecule which can be lost to give the odd-electron ion is to be stated.
Concept introduction:
Mass spectroscopy is used to calculate mass to charge ratio of ions. Isotopic peak is also known as
(c)
Interpretation:
The mechanism for the origin of each fragment ion is to be stated.
Concept introduction:
Mass spectroscopy is used to calculate mass to charge ratio of ions. Isotopic peak is also known as
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EBK ORGANIC CHEMISTRY
- A low-resolution mass spectrum of the neurotransmitter dopamine gave a molecular ion at m/z = 153. Two possible molecular formulas for this molecular ion are C8H11NO2 and C7H11N3O. A high-resolution mass spectrum provided an exact mass at 153.0680. Which of the possible molecular formulas is the correct one?arrow_forward(a) What would be the chemical shift of a peak that is observed at 655.2 Hz from the reference tetramethylsilane (TMS) recorded using a 90 MHz spectrometer ? (b) At what frequency would the chemical shift of chloroform (CHCl3, δ = 7.28 ppm) occur relative to TMS on a spectrum recorded on a 300 MHz spectrometer? (c) At what frequency and chemical shift would the signal for chloroform occur when using a 1 GHz NMR spectrometer?arrow_forwardchromophores as (b) Identify the indicated NMR entiotopic/diastereotopic/homotopic magnetically equivalent or non-equivalent. as well as CH₂ H CH3 HOCHI HH₂C (c) A tri-substituted benzene possessing one bromine and two methoxy substituents exhibit three aromatic resonances at d = 6.40, 6.46, and 7.41 ppm. Identify the substitution pattern.arrow_forward
- The mass spectrum of compound B is shown below. 100 180 80 181 77 В 182 20 104 25 50 75 100 125 150 175 200 m/z (i) Identify the molecular ion peak of compound B. (ii) Explain the peak at m/z 182 in terms of intensity. (iii) Explain the formation of the other labelled fragments (m/z 180, 104 and 77). Relative Intensityarrow_forward2,3-Dimethylbutane and 2,2-dimethylbutane have the same molecular ion in the mass spectrum, but only one of these isomers gives a significant fragment at m/z = 57. (a) Which isomer shows an intense peak at m/z = 57? (b) Propose a structure for the ion that gives rise to this peak. (c) The base peak in the mass spectrum of the other isomer occurs at m/z = 43. What ion gives rise to this peak?arrow_forwardThe mass spectrum of 1-propanol shows a large peak at m/z=31. Draw the structure of the fragment and explain why it is particularly stable.arrow_forward
- (a) Based on the mass spectrum shown below, 100 73 LOH 80 - A 58 20 - 100 10 20 30 40 50 60 70 80 90 100 110 m/z (i) identify the molecular ion peak of compound A. (ii) explain how the labelled fragments are formed. Relative Intensityarrow_forwardA student takes an IR spectrum of an unknown compound. The IR spectrum shows significant stretches at 3159 cm³¹ (m, sh), 3089 cm ¹ (m, sh), 3000 cm ¹ (m, sh), 2997 cm-¹ (m, sh), 1620 cm-¹ (s, sh), 1494 cm-¹ (s, sh), and 1210 cm-¹ (s, sh). Which possible compound is it? Key: S = Strong, M = Medium, W = Weak, Sh = Sharp, Br = Broad Anisole Aniline O Acetanilide O Acetone O Phenolarrow_forwardThe molecular ion peak in a mass spectrum of compound W appears at m/z = 107. Predict the molecular formula of compound W. (Hint: Compound W contains a heteroatom, not only carbon and hydrogen).arrow_forward
- The electron ionization (EI) mass spectrum of 2-hexanone (C6H12O, molecular weight 100.16) is shown below. Draw the structure responsible for the signal at m/z 58 and name the fragmentation mechanism involved.arrow_forwardAssigning Possible Structures to Fragments in a Mass Spectrum The mass spectrum of 2,3-dimethylpentane [(CH3)2CHCH(CH3)CH2CH3] shows fragments at m/z = 85 and 71. Propose possible structures for the ions that give rise to these peaks.arrow_forwardThe mass spectrum of n-octane shows a prominent molecular ion peak (m>z 114). There is also a large peak at m>z 57,but it is not the base peak. The mass spectrum of 3,4-dimethylhexane shows a smaller molecular ion, and the peak atmass 57 is the base peak. Explain these trends in abundance of the molecular ions and the ions at mass 57, and predict theintensities of the peaks at masses 57 and 114 in the spectrum of 2,2,3,3-tetramethylbutane.arrow_forward
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