Information about Optical Activity
Optical rotation or optical activity is the rotation of linearly polarized light as it travels through certain materials. It occurs in solutions of chiral molecules such as sucrose (sugar), solids with rotated crystal planes such as quartz, and spin-polarized gases of atoms or molecules. It is used in the sugar industry to measure syrup concentration, in optics to manipulate polarization, in chemistry to characterize substances in solution, and is being developed as a method to measure blood sugar concentration in diabetic people.
The rotation of the orientation of linearly polarized light was first observed in 1811 in quartz by French physicist Dominique F.J. Arago. Around this same time, Jean Baptiste Biot also observed the effect in liquids and gases of organic substances such as turpentine. In 1822, the English astronomer Sir Joun F.W. Herschel discovered that different crystal forms of quartz rotated the linear polarization in different directions. Simple polarimeters have been used since this time to measure the concentrations of simple sugars, such as glucose, in solution. In fact, one name for glucose, dextrose, refers to the fact that it causes linearly polarized light to rotate to the right or side. Similarly, levulose, more commonly known as fructose, causes the plane of polarization to rotate to the left. Fructose is even more strongly levorotatory than glucose is dextrorotatory. Invert sugar, formed by adding fructose to a solution of glucose, gets its name from the fact that the conversion causes the direction of rotation to "invert" from right to left.
In 1849, Louis Pasteur resolved a problem concerning the nature of tartaric acid. A solution of this compound derived from living things (specifically, wine lees) rotated the plane of polarization of light passing through it, but tartaric acid derived by chemical synthesis had no such effect, even though its reactions were identical and its elemental composition was the same. Pasteur noticed that the crystals came in two asymmetric forms that were mirror images of one another. Sorting the crystals by hand gave two forms of the compound: solutions of one form rotated polarized light clockwise, while the other form rotated light counterclockwise. An equal mix of the two had no polarizing effect on light. Pasteur deduced the molecule in question was asymmetric and could exist in two different forms that resemble one another as would left- and right-hand gloves, and that the organic form of the compound consisted purely of the one type.
In 1874, Jacobus Henricus van 't Hoff and Joseph Achille Le Bel independently proposed that the phenomenon of optical activity could be explained by assuming that the chemical bonds between carbon atoms and their neighbors were directed towards the corners of a regular tetrahedron. This led to a better understanding of the three-dimensional nature of molecules.
is the electric field of the light. The relative phase between the two circular polarizations, 
, sets the direction of the linear polarization to 
. In an optically active material the two circular polarizations experience different refractive indices. The difference in the indices quantifies the strength of the optical activity,
of material the two polarizations pick up a relative phase of
is the wavelength of the light (in vacuum). Consequently, the final polarization is rotated to angle 
.
Generally, the refractive index depends on the wavelength (see dispersion). The variation in rotation with the wavelength of the light is called optical rotatory dispersion (ORD). ORD spectra and circular dichroism spectra are related through the Kramers-Kronig relations. Complete knowledge of one spectrum allows the calculation of the other.
In summary, the degree of rotation depends on the color of the light (the yellow sodium D line near 589 nm wavelength is commonly used for measurements), the path length and the properties of the material (e.g. 
or specific rotation and concentration).
For a pure substance in solution, if the color and path length are fixed and the specific rotation is known, the observed rotation can be used to calculate the concentration. This usage makes a polarimeter a tool of great importance to those who trade in or use sugar syrups in bulk.
In the presence of magnetic fields all molecules have optical activity. A magnetic field aligned in the direction of light propagating through a material will cause the rotation of the plane of linear polarization. This Faraday effect is one of the first discoveries of the relationship between light and electromagnetic effects.
Optical activity or rotation should not be confused with circularly polarized light. Circularly polarized light is often presented as a linear polarization rotating as the light propagates. However, in this picture the polarization completely rotates in a length equal to the wavelength (roughly one micrometre) and it can happen in vacuum. In contrast, optical activity only occurs in a material and a complete rotation occurs in a length of millimeters to meters, depending on the material.
Tartaric acid is a white crystalline organic acid. It occurs naturally in many plants, particularly grapes, bananas, and tamarinds, and is one of the main acids found in wine. It is added to other foods to give a sour taste, and is used as an antioxidant.
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History
)
The two asymmetric crystals forms, dextro and levorotatory, of tartaric acid.
In 1849, Louis Pasteur resolved a problem concerning the nature of tartaric acid. A solution of this compound derived from living things (specifically, wine lees) rotated the plane of polarization of light passing through it, but tartaric acid derived by chemical synthesis had no such effect, even though its reactions were identical and its elemental composition was the same. Pasteur noticed that the crystals came in two asymmetric forms that were mirror images of one another. Sorting the crystals by hand gave two forms of the compound: solutions of one form rotated polarized light clockwise, while the other form rotated light counterclockwise. An equal mix of the two had no polarizing effect on light. Pasteur deduced the molecule in question was asymmetric and could exist in two different forms that resemble one another as would left- and right-hand gloves, and that the organic form of the compound consisted purely of the one type.
In 1874, Jacobus Henricus van 't Hoff and Joseph Achille Le Bel independently proposed that the phenomenon of optical activity could be explained by assuming that the chemical bonds between carbon atoms and their neighbors were directed towards the corners of a regular tetrahedron. This led to a better understanding of the three-dimensional nature of molecules.
Theory
Optical activity is a type of birefringence. Any linear polarization of light can be written as an equal combination of right-hand (RHC) and left-hand circularly (LHC) polarized light:
is the electric field of the light. The relative phase between the two circular polarizations, , sets the direction of the linear polarization to . In an optically active material the two circular polarizations experience different refractive indices. The difference in the indices quantifies the strength of the optical activity,
.
of material the two polarizations pick up a relative phase of
,
is the wavelength of the light (in vacuum). Consequently, the final polarization is rotated to angle .
Generally, the refractive index depends on the wavelength (see dispersion). The variation in rotation with the wavelength of the light is called optical rotatory dispersion (ORD). ORD spectra and circular dichroism spectra are related through the Kramers-Kronig relations. Complete knowledge of one spectrum allows the calculation of the other.
In summary, the degree of rotation depends on the color of the light (the yellow sodium D line near 589 nm wavelength is commonly used for measurements), the path length
and the properties of the material (e.g. or specific rotation and concentration).
Areas of use
For a pure substance in solution, if the color and path length are fixed and the specific rotation is known, the observed rotation can be used to calculate the concentration. This usage makes a polarimeter a tool of great importance to those who trade in or use sugar syrups in bulk.
In the presence of magnetic fields all molecules have optical activity. A magnetic field aligned in the direction of light propagating through a material will cause the rotation of the plane of linear polarization. This Faraday effect is one of the first discoveries of the relationship between light and electromagnetic effects.
Optical activity or rotation should not be confused with circularly polarized light. Circularly polarized light is often presented as a linear polarization rotating as the light propagates. However, in this picture the polarization completely rotates in a length equal to the wavelength (roughly one micrometre) and it can happen in vacuum. In contrast, optical activity only occurs in a material and a complete rotation occurs in a length of millimeters to meters, depending on the material.
References
- Eugene Hecht, Optics, 3rd Ed., Addison-Wesley, 1998, ISBN 0-201-30425-2
See also
linear polarization or plane polarization of electromagnetic radiation is a confinement of the electric field vector or magnetic field vector to a given plane along the direction of propagation. See polarization for more information.
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Light is electromagnetic radiation of a wavelength that is visible to the eye (visible light). In a scientific context, the word "light" is sometimes used to refer to the entire electromagnetic spectrum.
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The term chiral (pronounced /ˈkaɪɹ(ə)l̩/) is used to describe an object that is non-superimposable on its mirror image. In terms of chemistry, such objects are usually molecules.
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Sucrose (common name: table sugar, also called saccharose) is a disaccharide (glucose + fructose) with the molecular formula C12H22O11. Its systematic name is α-D-glucopyranosyl-(1→2)-β-D-fructofuranose.
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CRYSTAL is a quantum chemistry ab initio program, designed primarily for calculations on crystals (3 dimensions), slabs (2 dimensions) and polymers (1 dimension) using translational symmetry, but it can be used for single molecules.[1] It is written by V.R. Saunders, R.
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Quartz (from German Quarz [1]) is the second most common mineral in the Earth's continental crust, feldspar being the first.
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Spin polarization is the degree by which the spin, i.e. the intrinsic angular momentum of elementary particles, is aligned to a given direction. This property may pertain to the spin, hence to the magnetic moment, of conduction electrons in ferromagnetic metals, such as iron,
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Sugars, brown
Nutritional value per 100 g (3.5 oz)
Energy 0 kcal 0 kJ
Carbohydrates 97.33 g
- Sugars 96.21 g
- Dietary fiber 0 g
Fat 0 g
Protein 0 g
Water 1.77 g
Thiamin (Vit. B1) 0.
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Nutritional value per 100 g (3.5 oz)
Energy 0 kcal 0 kJ
Carbohydrates 97.33 g
- Sugars 96.21 g
- Dietary fiber 0 g
Fat 0 g
Protein 0 g
Water 1.77 g
Thiamin (Vit. B1) 0.
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Optics (ὀπτική appearance or look in Ancient Greek) is a branch of physics that describes the behavior and properties of light and the interaction of light with matter.
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polarization (Brit., polarisation) is the property of electromagnetic waves, such as light, that describes the direction of the transverse electric field. More generally, the polarization of a transverse wave describes the direction of oscillation in the plane
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Blood sugar is a term used to refer to the amount of glucose in the blood. Glucose, transported via the bloodstream, is the primary source of energy for the body's cells.
Blood sugar concentration, or glucose level, is tightly regulated in the human body.
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Blood sugar concentration, or glucose level, is tightly regulated in the human body.
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Diabetes mellitus
Classification & external resources
ICD-10 E 10. –E 14.
ICD-9 250
MedlinePlus 001214
eMedicine med/546 emerg/134
MeSH C18.452.394.
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Classification & external resources
ICD-10 E 10. –E 14.
ICD-9 250
MedlinePlus 001214
eMedicine med/546 emerg/134
MeSH C18.452.394.
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Quartz (from German Quarz [1]) is the second most common mineral in the Earth's continental crust, feldspar being the first.
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Jean-Baptiste Biot (April 21 1774, Paris – February 3 1862, Paris) was a French physicist, astronomer and mathematician. In the early 1800s, he studied the polarisation of light passing through chemical solutions, as well as the relationship between electrical current and
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Turpentine (also called spirit of turpentine, oil of turpentine, wood turpentine, gum turpentine) is a fluid obtained by the distillation of resin obtained from trees, mainly pine trees. It is composed of terpenes, mainly the monoterpenes alpha-pinene and beta-pinene.
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Polarimetry is the measurement of the polarisation of light; a polarimeter is the scientific instrument used to make these measurements. Polarimetry of thin films and surfaces is commonly known as ellipsometry.
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Glucose (Glc), a monosaccharide (or simple sugar), is an important carbohydrate in biology. The living cell uses it as a source of energy and metabolic intermediate.
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Fructose (or levulose) is a simple sugar (monosaccharide) found in many foods and is one of the three most important blood sugars along with glucose and galactose. Honey, tree fruits, berries, melons, and some root vegetables, such as beets, sweet potatoes, parsnips, and
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Louis Pasteur (December 27 1822 – September 28 1895) was a French chemist best known for his remarkable breakthroughs in microbiology. His experiments confirmed the germ theory of disease, also reducing mortality from puerperal fever (childbed), and he created the first
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Tartaric acid is a white crystalline organic acid. It occurs naturally in many plants, particularly grapes, bananas, and tamarinds, and is one of the main acids found in wine. It is added to other foods to give a sour taste, and is used as an antioxidant.
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Lees refers to deposits of dead yeast or residual yeast and other particles that precipitate, or are carried by the action of "fining", to the bottom of a vat of wine after fermentation and aging. The yeast deposits in beer brewing are known as Trub (brewing).
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polarization (Brit., polarisation) is the property of electromagnetic waves, such as light, that describes the direction of the transverse electric field. More generally, the polarization of a transverse wave describes the direction of oscillation in the plane
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In chemistry, chemical synthesis is purposeful execution of chemical reactions in order to get a product, or several products. This happens by physical and chemical manipulations usually involving one or more reactions.
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Jacobus Henricus van 't Hoff
Jacobus Henricus van 't Hoff
Born August 30, 1852
Rotterdam, Netherlands
Died March 1 1911 (aged 60)
Steglitz, Berlin, Germany
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Jacobus Henricus van 't Hoff
Born August 30, 1852
Rotterdam, Netherlands
Died March 1 1911 (aged 60)
Steglitz, Berlin, Germany
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Joseph Achille Le Bel (1847–1930), was a French Chemist, who was best known for his work in Stereochemistry. He was born on January 21 1847 in Péchelbronn and educated at the École Polytechnique in Paris.
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Birefringence, or double refraction, is the decomposition of a ray of light into two rays (the ordinary ray and the extraordinary ray) when it passes through certain types of material, such as calcite crystals or boron nitride, depending on the polarization of
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electric field. This electric field exerts a force on other electrically charged objects. The concept of electric field was introduced by Michael Faraday.
The electric field is a vector field with SI units of newtons per coulomb (N C−1
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The electric field is a vector field with SI units of newtons per coulomb (N C−1
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circular polarization (also circular polarisation) of electromagnetic radiation is a polarization such that the tip of the electric field vector, at a fixed point in space, describes a circle as time progresses.
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The refractive index (or index of refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves) is reduced inside the medium. For example, typical glass has a refractive index of 1.
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