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Organic Chemistry

Scorching goIITian

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9 Jun 2007 23:47:29 IST

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isomerism

Engineering Entrance , Medical Entrance , AIPMT , JEE Main , AIIMS , JEE Advanced , Chemistry , Organic Chemistry

hello all,

In isomerism, whaat does it mean by "optical activity "???...

I havent got the concept yet.....

Pls ,could anyone explain " OPTICAL ACTIVITY "

Comments (6)

meenal vig

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10 Jun 2007 17:17:00 IST

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the organic compound having chiral carbon can represent optical activity , which is the tendency to rotate plane polarised light

C , having four different groups attached with it is known as chiral carbon

..........specify if any perticular example, in which u have any problem

Akansha

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10 Jun 2007 18:00:14 IST

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Hi,

>>z cmpnds which rotate ppl by certain angle clockwise or ACW r non as opticly actve cmpnds n the phenomena is known as OPTICAL ACTIVITY.d n l r optically active cmpds (d(DEXTROROTATORY) rotates ppl ACW wile l(LAEVOROTATORY) rotates it CW ).Meso r optcally inactive

>>All opticali activ cmp show optical isomerism but the converse is nt true

>>CONDITION FR OPTICL ISOMERISM

-->Presence of at least 1 chiral C atms(a atm surrounded by 4 diff atms or grps)

--->non superimposable mirror image

>>CONDITION OF OPTICL ACTIVITY

---->absence of symmetry n presence of at least 1 chiral carbn atm

HOPE IT HELPS U !

JAYSUN ANTONY

Scorching goIITian

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11 Jun 2007 01:58:36 IST

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akku,

to be frank..........I couldnt get to that level in which u talk..........

could u make it simple ??........thnx

And chem4884,

thnx fr he expnation, though its brief.......

but i couldnt get """which is the tendency to rotate plane polarised light"""

Could u explain the phrase..........????

bumba

Scorching goIITian

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11 Jun 2007 02:22:39 IST

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optical activity is the tendency to rotate the plane polarised light either clockwise or anticlockwise.
as conditions and other theory is given above i won't be giving those again rather i am providing the mechanism for measuring the optical activity:::
first as u know ordinary light has its vibrations in different planes so it is first passes through nicol prism made of calcite and then passed through a polarimeter.the optical substance is placed at the end of the polarimeter and as this light falls on it it becomes dark.then an object such as a protractor type of thing placed at the end of polarimeter with the slit is rotated and when the bright light is again seen,that corresponding angle is the angle rotated by thelight due to the optical substance...
rate me if satisfied..........

meenal vig

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11 Jun 2007 11:14:30 IST

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when polychromatic light( group of lights having diff wavelengths ) is passed through specific filters,then only one type of light (of one wavelength) can pass through, all others get absorbed .........when this kind of light is passes through substance having chiral carbon, then it get rotated....either clockwise or anticlockwise....depending upon comparative arrangement of functional groups around this carbon.......this is optical activity..........(remember light will not get deflected from its path,...rather it only get rotated)

Khinar Thukral

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13 Jun 2007 23:33:04 IST

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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.The specific rotation of a chemical compound [?] is defined as the observed angle of optical rotation ? when plane-polarized light is passed through a sample with a path length of 1 decimeter and a sample concentration of 1 gram per 1 millilitre. 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 room temperature. The formal unit for specific rotation values is deg cm² g-1 but scientific literature uses just degrees. A negative value means levorotatory rotation and a positive value means dextrorotatory rotation. Some examples:A specific rotation is measeured by a polarizer which consists of a nicol prism.When the ordinary light is passed through the nicol prism then we obtain a polarized light which id passed through an organic compound which rotates the PLANE POLARIZED light to left(Laevorotatry) or right(Dextrorotatry).

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