2-Methylpentanal and 4-methyl-2-pentanone are constitutional isomers with themolecular formula C,H,,0. Each shows a molecular ion peak in its mass spectrum atmlz 100. Spectrum A shows significant peaks at mlz 85, 58, 57, 43, and 42. SpectrumB shows significant peaks at mlz 71, 58, 57, 43, and 29. Assign each compound itscorrect spectrum.`H2-Methylpentanal4-Methyl-2-pentanone

Draw the structure of give isomer of 2-Maethyl pentanal and 4- methyl-2-pentanone molecule. Above…

Answered: 2-Methylpentanal and…

Organic Chemistry

8th Edition

ISBN:9781305580350

Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote

Publisher:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote

Chapter21: Benzene And The Concept Of Aromaticity

Section: Chapter Questions

Problem 21.20P

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Here are proton NMR data for 1-bromopropane: Ha : triplet (2H) 3.32ppm; Hb : multiplet (2H)1.81ppm; Hc : triplet (3H) 0.93ppm. (Relative integrations shown in parentheses.) a. Through how many bonds can a hydrogen split another hydrogen? b. According to this splitting rule, does Ha split Hc ? c. Is your answer in part a) consistent with the multiplicity listed for peak clusters a and c? d. How many hydrogenssplit Hb ? e. Upon very close inspection of the proton NMR spectrum of 1-bromopropane, you wouldfind that peak cluster b has at least six peaks. Is this consistent with your answer in part d)? f. Speculate as to why any peak cluster with more than four peaks is listed simply as a"multiplet."
The integrated 1H NMR spectrum of a compound of formula C4H10O is shown in FIGURE 13-11. Propose a structure.
The mass spectrum and 13C NMR spectrum of a hydrocarbon are shown. Propose a structure for this hydrocarbon, and explain the spectral data.
The infrared spectrum of the compound with the mass spectrum shown below lacks any significant absorption above 3000 cm-1. There is a prominent peak near 1740 cm-1 and another strong peak near 1200 cm-1. Propose a structure consistent with the data.
Compound A, a hydrocarbon with M+=96 in its mass spectrum, has the 13C spectral data given below. On reaction with BH3, followed by treatment with basic H2O2. A is converted into B, whose, 13C spectral data are also given below. Propose structures for A and B. Compound A Broadband-decoupled l3C NMR: 26.8, 28.7, 35.7, 106.9, 149.7 DEPT-90: no peaks DEPT-135: no positive peaks; negative peaks at 26.8, 28.7, 35.7, 106.9 Compound B Broadband-decoupled 13C NMR: 26.1, 26.9, 29.9, 40.5, 68.2 DEPT-90: 40.5 DEPT-135: positive peak at 40.5 ; negative peaks at 26.1, 26.9. 29.9, 68.2
Long-range coupling between protons more than two carbon atoms apart is sometimes observed when bonds intervene. An example is found in 1-methoxy-l-buten-3-yne. Not only does the acetylenic proton, Î—a, couple with the vinylic proton Hb, it also couples with the vinylic proton Hc, four carbon atoms away. The data are: Construct tree diagrams that account for the observed splitting patterns of Î—a, Hb, and Hc.
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 butdistinctive mass spectra.O Obutyl propyl ether butyl isopropyl etherBoth compounds give prominent peaks at m>z 116, 73, 57, and 43. But one compoundgives 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.
Reaction of pentanoyl chloride (CH3CH2CH2CH2COCl) with lithium dimethyl cuprate [LiCu(CH3)2] forms a compound J that has a molecular ion in its mass spectrum at 100, as well as fragments at m/z = 85, 57, and 43 (base). The IR spectrum of J has strong peaks at 2962 and 1718 cm-1. Propose a structure for J.
Mass spectra of butylcyclopentane and tert-butylcyclopentane were acquired. Spectrum A exhibited significant mass peaks at m/z values of 126, 97, 83, 69, 55, and 41. Spectrum B exhibited significant peaks at m/z values of 111, 69,57, and 41. Match each spectrum with its compound.
The molecular ion in the mass spectrum of 2-methyl-1-pentene appears at m/z 84. Propose structural formulas for the prominent peaks at m/z 69, 55, 41, and 29.
2,3-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?
Oxidation of citronellol, a constituent of rose and geranium oils, with PCC in the presence of added NaOCOCH3 forms compound A. A has amolecular ion in its mass spectrum at 154 and a strong peak in its IRspectrum at 1730 cm−1, in addition to C—H stretching absorptions.Without added NaOCOCH3, oxidation of citronellol with PCC yieldsisopulegone, which is then converted to B with aqueous base. B has amolecular ion at 152 and a peak in its IR spectrum at 1680 cm−1, inaddition to C—H stretching absorptions. a.) Identify the structures of A and B.b.) Draw a mechanism for the conversion of citronellol to isopulegone.c.) Draw a mechanism for the conversion of isopulegone to B.

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