Concept explainers
Interpretation:
In the UV-vis. Spectrum of benzene, the absorption that corresponds to the HOMO-LUMO transition occurs at
Concept introduction:
In UV–vis. spectroscopy, absorption of a photon promotes an electron from a lower energy MO to a higher-energy MO.
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Organic Chemistry: Principles and Mechanisms (Second Edition)
- Carbon monoxide [CO] exhibits an IR absorption at 2143cm-1, acetone [CH3C(O)CH3],exhibits an IR absorption for the CO vibration at 1715 cm-1 and ethanol [CH3CH2OH] exhibits an IR absorption for CO at ~1150 cm-1. Draw Lewis structures of these three molecules and use your structures to explain the observed differences in the CO IR absorption peak frequency (nCO).arrow_forwardOrganic Chemistry: IR spectroscopy A student obtains an IR spectrum with an intense, broad absorption at about 3350 cm-1. The student claims that the sample is an alcohol, but the professor says that the absorption is there because the sample is contaminated with water. What peak(s) could be looked for to show that the sample is indeed an alcohol? Which functional groups would make it difficult to use this strategy?arrow_forwardWhat can be said about the ratios of the multiplet areas in the 13C spectra for trichloroethene; 1,2-dichloroethane; 1,1,1-trichloroethane; 1,1,2-trichloroethane.arrow_forward
- Why do aldehydes, esters, and amides all have a strong absorption in the 1630-1780 cm1 region of their IR spectra? A) The bond between H and the sp³-hybridized C in these functional groups vibrates in this energy range. B) Each of these functional groups has at least two resonance structures, and the different vibrations of the resonance structures give off energy in this region. C) The bond between O and the sp²-hybridized C in these functional groups vibrates at a frequency in this energy range. D) Light at this wavenumber causes the average C to O bond length to increase which causes more of this light to be transmitted. E) An electron in the bond of these functional groups gets excited to the * orbital.arrow_forwardThe infrared spectrum of 12Carbon and 16Oxygen shows an absorption peak at 2170cm^-1. What is the bond strength constant at 12c16o and predict the expected frequency at 13c17o assuming the strength constant does not change.arrow_forwardThe beer-lambert law is A = εlc, where A is the absorbance, ε is the molar extinction coefficient, l is the path lengh in cm and C is the concentration. The beer lambert law can be expressed in the form of y=mx + b, where A is y, and C is x.What is b and how is it used to calculate the final absorbance?arrow_forward
- The functional groups in an organic compound can frequently be deduced from its infrared absorption spectrum. A compound containing C, H, and O exhibits broad absorption at 3450 cm-1 (m) and an intense band at 1725, plus a band at 1100 cm-1 (m).Relative absorption intensity: (s)=strong, (m)=medium, (w)=weak. What functional class(es) does the compound belong to? List only classes for which evidence is given here. Attach no significance to evidence not cited explicitly.Do not over-interpret exact absorption band positions. None of your inferences should depend on small differences like 10 to 20 cm-1. The functional class(es) of this compound is(are)fill in the blank 1.(Enter letters from the table below, in any order, with no spaces or commas.) a. alkane (List only if no other functional class applies.) b. alkene h. amine c. terminal alkyne i. aldehyde or ketone d. internal alkyne j. carboxylic acid e. arene k. ester f. alcohol l. nitrile g. etherarrow_forwardWhat IR frequencies would enable a chemist to distinguish between these molecules? CH;CH2OH and CH;CH2OCH;CH3 and CH, HCHCHCCIICH CH, d 3000-3100 cm-1 (=C-H)| 1620-1680 cm-1 (C=C) 3200-3400 cm-1 (OH) || 3000-3100 cm-1 (=C-H)arrow_forwardThe functional groups in an organic compound can frequently be deduced from its infrared absorption spectrum. A compound contains no nitrogen and exhibits absorption bands at 3300 (s) and 2150 (m) cm ¹¹. Relative absorption intensity: (s)=strong, (m)=medium, (w)=weak. What functional class(es) does the compound belong to? List only classes for which evidence is given here. Attach no significance to evidence not cited explicitly. Do not over-interpret exact absorption band positions. None of your inferences should depend on small differences like 10 to 20 cm³¹. The functional class(es) of this compound is(are) . (Enter letters from the table below, in any order, with no spaces or commas.) a. alkane (List only if no other functional class applies.) b. alkene c. terminal alkyne d. internal alkyne e. arene f. alcohol g. ether Submit Answer h. amine i. aldehyde or ketone j. carboxylic acid k. ester I. nitrile Retry Entire Group 9 more group attempts remainingarrow_forward
- 3. Identify C-Cl stretching peaks in CDC13 and CHC13 spectra. Do these peaks have exactly the same frequencies for both compounds? Explain your answer. 4. Is the C==O stretching frequency the same for acetone and deuterated acetone? Explain your answer. 5. Identify C==O overtone in acetone spectrum which corresponds to the transition from ground level, n=0, to the second excited level, n=2.arrow_forwardThe infrared absorption spectrum of 12C14N has its strongest band at 2500 cm-1 wavenumber. Calculate the force constant (N/m) of the bond in this molecule.arrow_forwardThe IR spectrum below belongs to an organic compound A having one nitrogen atom. Determine which structures that fits to the IR spectrum. Justify your answer by providing two (2) IR absorption peaks with their wavenumber. CN NH2 Ahsorbance / 4 50 100- 4000 3000 2500 2000 1500 1000 500 Wavenumbers / cmarrow_forward
- Organic ChemistryChemistryISBN:9781305580350Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. FootePublisher:Cengage Learning