1 翻译
Spectroscopy mass Spectroscopy
ultravlolet-visible specrometry infrered spectrosopy nuclear magnetic Resonance spectroscopy electromagnetic spectrum wave-like and particle-like Fragmentation pattern excited state bathochromic 2 命名
Bromine vinyl chloride methylene chloride ether alcohol ketone,4-methyl-3pentene-2-one ethane propane butane pentane 3翻译
In order to measure the characteristics of individual molecules, a mass spectrometer converts them to ions so that they can be moved about and manipulated by external electric and magnetic fields.
Some of these ions fragment into smaller cations and neutral fragments. When the ion beam experiences a strong magnetic field perpendicular to its direction of motion, the ions are deflected in an arc whose radius is inversely proportional to the mass of the ion.
Modern mass spectrometers easily distinguish (resolve) ions differing by only a single atomic mass unit (amu), and thus provide completely accurate values for the molecular mass of a compound.
The fragmentation of molecular ions into an assortment of fragment ions is a mixed blessing.
Among simple organic compounds, the most stable molecular ions are those from aromatic rings, other conjugated pi-electron systems and cycloalkanes.
The presence of chromophores in a molecule is best documented by UV-Visible spectroscopy, but the failure of most instruments to provide absorption data for wavelengths below 200 nm makes the detection of isolated chromophores problematic.
Most infrared spectra are displayed on a linear frequency scale, as shown here, but in some older texts a linear wavelength scale is used.
Perchlorinated solvents such as carbon tetrachloride, chloroform and tetrachloroethene are commonly used.
it is more common to use a frequency scale, even though the spectrometer may operate by sweeping the magnetic field.
Since no two magnets will have exactly the same field, resonance frequencies will vary accordingly and an alternative method for characterising and specifying the location of nmr signals is needed.
完形填空
Radio_____[ frequency ]radiation of appropriate energy is broadcast into the sample from an_____[ antenna] coil (colored red). A receiver coil surrounds the sample tube, and emission of absorbed rf energy is_____[ monitored] by dedicated electronic devices and a computer. An nmr____[ spectrum] is acquired by varying or sweeping the magnetic field over a small range while observing the rf signal from the sample. An equally effective technique is to vary the frequency of the rf_____[ radiation] while holding the external field constant.
选择题
1. What is the light characterized ?
A. wave-like characteristic B. particle-like characteristic C. wave-like and particle-like characteristics
2.What is the heart of mass spectrometer?
A . Ion source B . Mass analyzer C . Detector
3. Visible wavelengths cover a range from approximately _____nm.
A .300 to 500 B . 500 to 1200 C . 400 to 800
4. Among simple organic compounds, the most stable molecular ions is____?
A. aromatic rings B. Cycloalkanes C. Olefin
5.Which of the following compounds can be spectroscopic study?
A. pure alcohol and ether solvents B.Methane and pure alcohol C. Methane and ether solvents
答案：cacaa