|
|
| Line 1: |
Line 1: |
| {{Multiple issues|refimprove =October 2010|technical =October 2010|lead rewrite =January 2013}}
| | == only to create a miniature universe as battlefield == |
|
| |
|
| In [[stereochemistry]], the '''specific rotation''' ('''[α]''') is an [[Intensive and extensive properties|intensive property]] of a [[chemical compound]], defined as the change in orientation of the plane of [[Linear polarization|linearly polarized light]] as this light passes through a sample with a path length of 1 [[decimetre|decimeter]] and a sample concentration of 1 [[gram]] per 1 [[millilitre]]. It is the main property used to quantify the [[chirality (chemistry)|chirality]] of a molecular species or a mineral. The specific rotation of a pure material is an intrinsic property of that material at a given wavelength and temperature. Values should always be accompanied by the temperature at which the measurement was performed and the solvent in which the material was dissolved. Often the temperature is not specified; in these cases it is assumed to be standard room temperature (20°C). The formal unit for specific rotation values is deg dm<sup>−1</sup>cm<sup>3</sup> g<sup>−1</sup> but scientific literature uses just [[degree (angle)|degrees]].<ref name=techniques1/> A negative value means [[levorotatory]] rotation and a positive value means [[dextrorotatory]] rotation. Dextrorotatory means that the plane of polarization is turned clockwise when the light comes through the sample to the observer.
| | Universe ', and Feng Luo talent Arcane' My universe 'miniature universe is not the same, Luo Feng Arcane talent that is too simple and pure moment eternal God created a miniature universe, pure energy is [http://www.nrcil.net/fancybox/lib/rakuten_LV_86.html ルイヴィトン ハンドバッグ] not enough, you can not come up with much universe, only to create a miniature universe as battlefield<br><br>such a move the hearts of thousands of light years around it into a miniature universe within<br><br>eternal God, is the owner [http://www.nrcil.net/fancybox/lib/rakuten_LV_89.html ルイヴィトンモノグラムバック] of this miniature [http://www.nrcil.net/fancybox/lib/rakuten_LV_34.html ルイヴィトン カバン メンズ] universe<br>This is in [http://www.nrcil.net/fancybox/lib/rakuten_LV_96.html ルイヴィトン 鞄] addition to the minimum volume<br>outside, and all the other wonders of the universe really no difference, big enough to make Vaillant's ...... eternal God has absolute void God's strength to sweep<br><br>......<br><br>true God, the void true God, eternal God<br><br>is one pair of 'Evolution of the wonders of the universe' deepening [http://www.nrcil.net/fancybox/lib/rakuten_LV_88.html ルイヴィトン ライン] process control until late an idea to create [http://www.nrcil.net/fancybox/lib/rakuten_LV_93.html ルイヴィトン 肩掛けバッグ] a small universe to<br>World<br>entire Jin, [http://www.nrcil.net/fancybox/lib/rakuten_LV_26.html ルイヴィトン スピーディ] a total of four eternal God<br><br>is Dong Jun, the West Army, Northern army, the four generals of his [http://www.nrcil.net/fancybox/lib/rakuten_LV_61.html ルイヴィトン カバン] army south |
| | | 相关的主题文章： |
| ==Measurement==
| | <ul> |
| Optical rotation is measured with an instrument called a [[polarimeter]]. There is a linear relationship between the observed rotation and the concentration of [[optical rotation|optically active]] compound in the sample. There is a nonlinear relationship between the observed rotation and the wavelength of light used. Specific rotation is calculated using either of two equations, depending on whether the sample is a pure chemical to be tested or that chemical dissolved in solution.
| | |
| | | <li>[http://bbs.mbqban.com/home.php?mod=space&uid=224903 http://bbs.mbqban.com/home.php?mod=space&uid=224903]</li> |
| ===For pure liquids===
| | |
| This equation is used:
| | <li>[http://sgirl.myyel.com/plus/feedback.php?aid=4 http://sgirl.myyel.com/plus/feedback.php?aid=4]</li> |
| | | |
| :<math>[\alpha]_\lambda^T = \frac{\alpha}{l \times \rho}</math>
| | <li>[http://www.yamaguchi-clinic.com/cgi-bin/bbs/joyful.cgi http://www.yamaguchi-clinic.com/cgi-bin/bbs/joyful.cgi]</li> |
| | | |
| In this equation, α (Greek letter "alpha") is the measured rotation in degrees, ''l'' is the path length in decimeters, and ''ρ'' (Greek letter "rho") is the density of the liquid in g/mL, for a sample at a temperature ''T'' (given in degrees Celsius) and wavelength ''λ'' (in nanometers). If the wavelength of the light used is 589 [[nanometers]] ([[Sodium-vapor_lamp#Low-pressure_sodium|the sodium D line]]), the symbol “D” is used. The sign of the rotation (+ or −) is always given.
| | </ul> |
| | |
| :<math>[\alpha]_D^{20} = +6.2</math>°
| |
| | |
| ===For solutions===
| |
| A different equation is used:
| |
| | |
| :<math>[\alpha]_\lambda^T = \frac{ \alpha}{l \times c}</math>
| |
| | |
| In this equation, α (Greek letter "alpha") is the measured rotation in degrees, ''l'' is the path length in decimeters and ''c'' is the concentration in g/mL, for a sample at a temperature ''T'' (given in degrees Celsius) and wavelength ''λ'' (in nanometers).<ref name=techniques1>{{cite book |title= Techniques in Organic Chemistry |edition= Third |publisher= W. H. Freeman and Company |year= 2010 |pages=209–210 |author= Mohrig, J. R.; Hammond, C. N.; Schatz, P. F. }}</ref> If the wavelength of the light used is 589 [[nanometer]] (the sodium D line), the symbol “D” is used. The sign of the rotation (+ or −) is always given.
| |
| When using this equation, the concentration and the solvent may be provided in parentheses after the rotation. The rotation is reported using degrees, and no units of concentration are given (it is assumed to be g/100mL).
| |
| | |
| For example:
| |
| | |
| :<math>[\alpha]_D^{20} = +6.2</math>° (c 1.0, EtOH)
| |
| | |
| ===Dealing with large and small rotations===
| |
| If a compound has a very large specific rotation or a sample is very concentrated, the actual rotation of the sample may be larger than 180°, and so a single polarimeter measurement cannot detect when this has happened (for example, the values +270° and −90° are not distinguishable, nor are the values 361° and 1°). In these cases, measuring the rotation at several different concentrations allows one to determine the true value. Another method would be to use shorter path-lengths to perform the measurements.
| |
| | |
| In cases of very small or very large angles, one can also use the variation of specific rotation with wavelength to facilitate measurement. Switching wavelength is particularly useful when the angle is small. Many polarimeters are equipped with a mercury lamp (in addition to the sodium lamp) for this purpose.
| |
| | |
| ===Absolute configuration===
| |
| The variation of specific rotation with wavelength is called [[optical rotatory dispersion]] (ORD). ORD can be used to elucidate the absolute configuration of certain compounds.
| |
| | |
| ===Mixtures===
| |
| Measuring optical rotation provides, in theory, a way to assess optical purity of a sample containing a mixture of enantiomers. For example, if a sample of bromobutane measured under standard conditions has an observed rotation of −9.2°, this indicates that the net effect is due to (100%)(9.2°/23.1°)=40% of the R [[enantiomer]]. The remainder of the sample is a [[racemic]] mixture of the enantiomers (30% R and 30% S), which has no net contribution to the observed rotation. The [[enantiomeric excess]] is 40%; the total concentration of R is 70%. However, in practice the utility of this method is limited, as the presence of small amounts of highly rotating impurities can greatly affect the rotation of a given sample. Moreover, the optical rotation of a compound may be non-linearly dependent on its enantiomeric excess because of aggregation in solution. For these reasons other methods of determining the enantiomeric ratio such as [[gas chromatography]] or [[high-performance liquid chromatography|HPLC]] with a chiral column is generally preferred.
| |
| | |
| ==Examples==
| |
| *(S)-[[2-Bromobutane]] +23.1°
| |
| *(R)-2-Bromobutane −23.1°
| |
| *D-[[Fructose]] −92.4°
| |
| *D-[[Glucose]] +52.5°
| |
| *D-[[Sucrose]] +66.47°
| |
| *D-[[Lactose]] +52.3°
| |
| *[[Camphor]] +44.1°
| |
| *[[Cholesterol]] −31.5°
| |
| *[[Paclitaxel]] −49°
| |
| *[[Penicillin V]] +223°
| |
| *(+)-[[Cavicularin]] +168.2°
| |
| *[[Hexol]] bromocamphorsulphonate 2640°<ref>A. Werner "Über mehrkernige Metallammoniake" Chem. Ber. 1907, volume 40, pp. 2103–2125. {{DOI|10.1002/cber.190704002126}}</ref>
| |
| All values are given in units of deg dm<sup>−1</sup>cm<sup>3</sup> g<sup>−1</sup>.
| |
| | |
| ==References==
| |
| {{Reflist}}
| |
| | |
| {{DEFAULTSORT:Specific Rotation}}
| |
| [[Category:Chemical properties]]
| |
only to create a miniature universe as battlefield
Universe ', and Feng Luo talent Arcane' My universe 'miniature universe is not the same, Luo Feng Arcane talent that is too simple and pure moment eternal God created a miniature universe, pure energy is ルイヴィトン ハンドバッグ not enough, you can not come up with much universe, only to create a miniature universe as battlefield
such a move the hearts of thousands of light years around it into a miniature universe within
eternal God, is the owner ルイヴィトンモノグラムバック of this miniature ルイヴィトン カバン メンズ universe
This is in ルイヴィトン 鞄 addition to the minimum volume
outside, and all the other wonders of the universe really no difference, big enough to make Vaillant's ...... eternal God has absolute void God's strength to sweep
......
true God, the void true God, eternal God
is one pair of 'Evolution of the wonders of the universe' deepening ルイヴィトン ライン process control until late an idea to create ルイヴィトン 肩掛けバッグ a small universe to
World
entire Jin, ルイヴィトン スピーディ a total of four eternal God
is Dong Jun, the West Army, Northern army, the four generals of his ルイヴィトン カバン army south
相关的主题文章：