Concept explainers
Cyclohexnone exhibits its strongest IR absorption hand at 5.86
(a) Identify the part of the molecule responsible for the absorbance at this wavelength.
(b) Suggest a solvent that would be suitable for a quantitative analysis of cyclohexanone at this wavelength.
(c) A solution of cyclohexanone (4.0 mg/mL) in the solvent selected in part (b) exhibits a blank-corrected absorbance of 0.800 in a cell with a path length of 0.025 mm. What is the detection limit for this compound under these conditions if the noise associated with the spectrum of the solvent is 0.001 absorbance units?
(a)
Interpretation:
The part of the molecule that is responsible for absorbance at the given wavelength is to be stated.
Concept introduction:
The IR absorption spectroscopy makes use of a mid infrared light that detects the particular types of chemical bonds in a given sample for the purpose of the identification of organic and organomettalic compounds. In the IR absorption spectra, there are two regions: Functional group region and the fingerprint region.
Answer to Problem 17.1QAP
The part of the molecule that is responsible for absorbance at the given wavelength is Carbonyl (
Explanation of Solution
Given information:
The IR absorption band is
The expression for the wave number is:
Here, the wavelength is
Substitute
(b)
Interpretation:
A solvent that would be suitable for quantitative analysis of cyclohexanone at the given wavelength is to be stated.
Concept introduction:
Quantitative analysis refers to the determination of relative or absolute quantity of a substance in a given sample. There are several methods of carrying out the quantitative analysis of the samples. These methods include gravimetric and volumetric analysis.
Answer to Problem 17.1QAP
A solvent that would be suitable for quantitative analysis of cyclohexanone at the given wavelength is cyclohexane and any chlorinated solvent.
Explanation of Solution
The solvent that is suitable for quantitative analysis of cyclohexanone at the given wavelength should be cheap and less toxic in nature.
The solvents that can be used are cyclohexane and any chlorinated solvent.
(c)
Interpretation:
The detection limit for the compound is to be stated.
Concept introduction:
The detection limit refers to the smallest quantity of the substance that can be differentiated from the absence of that particular substance with a certain level of confidence.
Answer to Problem 17.1QAP
The detection limit for the compound is
Explanation of Solution
Given information:
Noise associated with the spectrum of the solvent is 0.001 absorbance units.
The expression for the Beer’s Law,
Here, the absorbance is
Substitute
Substitute
Divide Equation (III) by Equation (II)
Want to see more full solutions like this?
Chapter 17 Solutions
Principles of Instrumental Analysis
- The 1H NMR spectrum of 1,2-dimethoxyethane (CH3OCH2CH2OCH3) recorded on a 300 MHz NMR spectrometer consists of signals at 1017 Hz and 1065 Hz downeld from TMS. (a) Calculate the chemical shift of each absorption. (b) At what frequency would each absorption occur if the spectrum were recorded on a 500 MHz NMR spectrometer?arrow_forward(b) Determine the structure of an organic compound with a molecular ion at m/z 73 and absorption in its IR at 3300 (doublet) and 1680 cmarrow_forwardWhen the 1î-NMR spectrum of acetone, CH3COCH3, is recorded on an instrument operating at 200 MHz, a single sharp resonance at 2.1î is seen. (a) How many hertz downfield from TMS does the acetone resonance correspond to? (b) If the 1î-NMR spectrum of acetone were recorded at 500 MHz, what would the position of the absorption be in î units? (c) How many hertz downfield from TMS does this 500 MHz resonance correspond to?arrow_forward
- 1 (c) 2-Methyl-3-pentanol reacts with PCC to form compound F. (i) Draw the structure of F. (ii) In the mass spectrum, identify the m/z value of the molecular ion peak for compound F. (ii) Fragmentation of radical cation F exhibits two fragment ion peaks at m/z 57 and m/z 71. Propose the structures of these two fragments. (iv) Draw the resonance structure for each of the cation in (iii).arrow_forwardA common lab experiment is the dehydration of cyclohexanol to cyclohexene.(a) Explain how you could tell from the IR spectrum whether your product was pure cyclohexene, pure cyclohexanol,or a mixture of cyclohexene and cyclohexanol. Give approximate frequencies for distinctive peaks.arrow_forward(a) Based on the information provided, determine the structures of compounds. (b) Assign all peaks in 1 H and 13C NMR spectra of compoundsarrow_forward
- Predict the theoretical number of different NMR signals produced by each compound, and give approximate chemical shifts. Point out any diastereotopic relationships. (a) Ph¬CHBr¬CH2Br (b) vinyl chloridearrow_forwardTreatment of alcohol A (molecular formula C5H12O) with CrO3, H2SO4, and H2O affords B with molecular formula C5H10O, which gives an IR absorption at 1718 cm−1. The 1H NMR spectrum of B contains the following signals: 1.10 (doublet, 6 H), 2.14 (singlet, 3 H), and 2.58 (septet, 1 H) ppm. What are the structures of A and B?arrow_forwardA'2 The 'H-NMR spectra of cyclohexanol and cyclohexanone are given below. Identify which spectrum belongs to which compound and assign the peaks in each spectrum that substantiate your decision.arrow_forward
- 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?arrow_forwardDraw the H1 NMR spectra of ethylcyclopropane. Draw the chemical structure and predict the proton splitting and chemical shifts.arrow_forwardIndicate two basic differences that exist between the spectra of 1H y 13C in NMR.arrow_forward
- ChemistryChemistryISBN:9781305957404Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCostePublisher:Cengage LearningChemistryChemistryISBN:9781259911156Author:Raymond Chang Dr., Jason Overby ProfessorPublisher:McGraw-Hill EducationPrinciples of Instrumental AnalysisChemistryISBN:9781305577213Author:Douglas A. Skoog, F. James Holler, Stanley R. CrouchPublisher:Cengage Learning
- Organic ChemistryChemistryISBN:9780078021558Author:Janice Gorzynski Smith Dr.Publisher:McGraw-Hill EducationChemistry: Principles and ReactionsChemistryISBN:9781305079373Author:William L. Masterton, Cecile N. HurleyPublisher:Cengage LearningElementary Principles of Chemical Processes, Bind...ChemistryISBN:9781118431221Author:Richard M. Felder, Ronald W. Rousseau, Lisa G. BullardPublisher:WILEY