Ultraviolet and Visible Spectra Quiz
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Questions and Answers

Which edition of 'Spectroscopic Methods in Organic Chemistry' is mentioned?

  • Seventh Edition (correct)
  • Fifth Edition
  • Eighth Edition
  • Sixth Edition

    • The book was published by McGraw-Hill Education.

    False

    Who are the authors of 'Spectroscopic Methods in Organic Chemistry'?

    Ian Fleming and Dudley Williams

    The book provides guidance on interpreting the mass, ultraviolet, infrared, and _______ spectra of organic compounds.

    <p>nuclear magnetic resonance</p> Signup and view all the answers

    Match the following keywords with their corresponding definitions:

    <p>Mass Spectrum = A plot showing the distribution of ions by mass-to-charge ratio Ultraviolet Spectrum = The spectrum obtained by passing UV light through a sample Infrared Spectrum = A spectrum representing the molecular vibrations Nuclear Magnetic Resonance = A technique to observe local magnetic fields around atomic nuclei</p> Signup and view all the answers

    What is NOT included in the methods discussed in the book?

    <p>Thermal Spectroscopy</p> Signup and view all the answers

    'Spectroscopic Methods in Organic Chemistry' is solely for advanced chemistry students.

    <p>False</p> Signup and view all the answers

    What is the ISBN number of the eBook version?

    <p>978-3-030-18252-6</p> Signup and view all the answers

    What does the term 'chromophore' refer to?

    <p>The system containing the electrons responsible for absorption</p> Signup and view all the answers

    A transition of an electron from a higher-energy orbital to a lower-energy orbital creates a singlet ground state.

    <p>False</p> Signup and view all the answers

    What is the significance of the absorption value 297 nm in organic compounds?

    <p>It is equivalent to 400 kJ or approximately 96 kcal, enough to initiate many reactions.</p> Signup and view all the answers

    The energy separation is related to wavelength by the equation E = _____, where E is measured in kJ/mol and 𝜆 is in nm.

    <p>1.19 × 10^5 / λ</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Electronic transition = Movement of an electron from lower to higher energy Ground state = Lowest energy state of an electron in an atom Excited state = Higher energy state after absorption of energy Wavelength = Distance between successive peaks of a wave</p> Signup and view all the answers

    Which of the following statements about electronic transitions is true?

    <p>They involve a promotion of electrons from filled to unfilled orbitals.</p> Signup and view all the answers

    Organic compounds should be left in the ultraviolet beam for extended periods.

    <p>False</p> Signup and view all the answers

    What range of wavelengths corresponds to the absorption due to σ bonds in chromophores?

    <p>120–150 nm</p> Signup and view all the answers

    What is the typical maximum wavelength (εmax) mentioned for forbidden transitions?

    <p>210 nm</p> Signup and view all the answers

    Ultraviolet spectroscopy is primarily used for structure determination rather than following chemical kinetics.

    <p>False</p> Signup and view all the answers

    What is the primary application of ultraviolet spectroscopy mentioned in the content?

    <p>Following the kinetics of a chemical reaction</p> Signup and view all the answers

    The set of books, __________, is considered the best source for UV and visible spectroscopic data.

    <p>Organic Electronic Spectral Data</p> Signup and view all the answers

    What does ACD stand for in ACD/SpecManager?

    <p>Advanced Chemistry Development</p> Signup and view all the answers

    Match the following websites with their descriptions:

    <p>NIST = Contains a database of 1600 compounds with UV data ACD Labs = Sells software for spectroscopy analysis Wiley-VCH = Provides up-to-date information about spectroscopic books Spectroscopy Now = Offers a directory for spectroscopy information</p> Signup and view all the answers

    Some websites may require specific __________ to function properly.

    <p>operating systems</p> Signup and view all the answers

    Provide the URL for the NIST website mentioned.

    <p><a href="http://webbook.nist.gov/chemistry/name-ser.html">http://webbook.nist.gov/chemistry/name-ser.html</a></p> Signup and view all the answers

    What is the primary advantage of using mass spectrometry for analyzing trace materials?

    <p>It can detect very small quantities of substances.</p> Signup and view all the answers

    Mass spectrometry requires at least milligram quantities of a sample to produce reliable data.

    <p>False</p> Signup and view all the answers

    Name one application of mass spectrometry in medical research.

    <p>Detection of drugs and their metabolites.</p> Signup and view all the answers

    Mass spectrometry is especially important for analyzing materials such as __________, atmospheric pollutants, and pesticides.

    <p>pheromones</p> Signup and view all the answers

    Match the molecular formula to its common inference.

    <p>C5H11+ = C5H11 —X C3H7CO+ = Propyl ketone, butyrate ester C4H9O+ = Possible ether or alcohol C6H4+ = C6H5 —X, X—C6H4 —Y</p> Signup and view all the answers

    Which mass spectrometry instrument characteristic is most significant in the context of molecular fragment production?

    <p>The method used to induce fragmentation.</p> Signup and view all the answers

    Mass spectrometry can be used to analyze changes in tissue samples during surgery.

    <p>True</p> Signup and view all the answers

    What is the significance of detecting cancerous tissue during surgery?

    <p>To ensure complete removal of cancerous cells.</p> Signup and view all the answers

    Mass spectrometry is used to analyze various molecules, typically those with a molecular weight of __________ or less.

    <p>relatively low</p> Signup and view all the answers

    Match the following ions to their possible inferences.

    <p>C6H7O+ = X—C6H7—O C7H8+ = C6H5 CH2—alkyl C5H5S+ = S—X C5H6N+ = N—X</p> Signup and view all the answers

    Which of the following shows a functional group associated with m/z 73?

    <p>C3H7CO+</p> Signup and view all the answers

    All instruments used in mass spectrometry analyze ions in the same way.

    <p>False</p> Signup and view all the answers

    What types of samples can be analyzed using mass spectrometry?

    <p>Trace materials, tissue samples, drugs, pollutants, and pesticides.</p> Signup and view all the answers

    Mass spectrometry can help identify __________ in environmental samples.

    <p>atmospheric pollutants</p> Signup and view all the answers

    What is the approximate absorption range for C=N double bonds?

    <p>1690–1630 cm−1</p> Signup and view all the answers

    C=C double bonds absorb at frequencies lower than C=N double bonds.

    <p>False</p> Signup and view all the answers

    What effect does conjugation have on the stretching frequency of C=C double bonds?

    <p>It lowers the stretching frequency slightly.</p> Signup and view all the answers

    Oleol 29 contains a cis double bond that is __________ detectable in the infrared spectrum.

    <p>weakly</p> Signup and view all the answers

    What happens to the intensity of C=C absorption when the double bond is symmetrically substituted?

    <p>It may be very weak or absent.</p> Signup and view all the answers

    Match the following compounds with their specific characteristics:

    <p>Ethyl crotonate = Moderately strong peak at 1665 cm−1 Vinyl acetate = Strong band at low end of C=C range Oleol 29 = Stretching is only just detectable C=C double bond in a ring = Frequency falls as ring size decreases</p> Signup and view all the answers

    Where does the C=C stretching vibration appear in the spectrum of vinyl esters?

    <p>At the low end of the C=C range.</p> Signup and view all the answers

    The more substituted C=C double bonds absorb at the __________ end of the frequency range.

    <p>high-frequency</p> Signup and view all the answers

    Study Notes

    Ultraviolet and Visible Spectra

    • Ultraviolet and Visible (UV-Vis) spectra are created by transitions between electronic energy levels, promoting an electron from a lower-energy orbital to a higher-energy orbital.
    • The wavelength of the absorption is related to the energy difference between the ground and excited states.
    • An absorption of 297 nm is equivalent to 400 kJ/mol, enough energy to initiate chemical reactions.
    • This means that samples should not be exposed to ultraviolet light for extended periods.

    Chromophores

    • A chromophore is the group of electrons responsible for the absorption of UV-Vis light.
    • Sigma (σ) bond electrons are excited by the shortest wavelength absorption, in the range of 120-150 nm.
    • Pi (π) bond electrons are excited by a slightly longer wavelength, typically around 180-200 nm.
    • The absorption of a non-conjugated system is weak and often masked by other absorptions.

    Conjugation and Absorption

    • Conjugation of double bonds results in a shift of the absorption wavelength to longer wavelengths.
    • This is because conjugation lowers the energy difference between the ground and excited states.
    • UV-Vis spectroscopy is a valuable tool for following the kinetics of reactions, especially those involving conjugated systems.
    • This is because the spectrum changes as the reaction progresses.

    Applications of UV-Vis Spectroscopy

    • UV-Vis spectroscopy has numerous applications in chemistry, including:
      • Determining concentration of molecules in solution
      • Monitoring reaction progress
      • Identifying functional groups
      • Detecting impurities

    Internet Resources

    • The National Institute of Standards and Technology (NIST) website provides a database of UV-Vis spectra for over 1600 compounds.
    • ACD/SpecManager is a proprietary software application that can process and store UV-Vis spectra. It also offers access to free databases of spectra.
    • Wiley-VCH provides an online resource for spectroscopic information, including that related to UV-Vis spectroscopy.
    • Organic Electronic Spectral Data is a comprehensive collection of UV-Vis spectra.

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    Related Documents

    Spectroscopic Methods in Organic Chemistry PDF

    Description

    Test your knowledge on the principles of ultraviolet and visible spectra, including the role of chromophores and the effects of conjugation on absorption. This quiz covers key concepts such as energy transitions, wavelength absorption, and the relevance of electronic energy levels in chemical reactions.

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