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Rot. spec.

English translation: specific rotation

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GLOSSARY ENTRY (DERIVED FROM QUESTION BELOW)
Italian term or phrase:Rot. spec.
English translation:specific rotation
Entered by: Julianne Rowland
Options:
- Contribute to this entry
- Include in personal glossary

17:21 Jul 7, 2007
Italian to English translations [PRO]
Science - Chemistry; Chem Sci/Eng / Material Safety Data Sheet
Italian term or phrase: Rot. spec.
Anyone who has been following my many postings knows that I am in somewhat unfamiliar territory with this job - thank you in advance for any suggestions.

This is from a MSDS in the Physical and Chemical Properties section and appears in context below:

Rot. spec. [a] 20º/D:

+ 289º (c=0,l in metanolo)

Any ideas, anyone?
Julianne Rowland
United States
Local time: 15:48
specific rotation
Explanation:
This is the rotation caused by chiral molecules


--------------------------------------------------
Note added at 9 mins (2007-07-07 17:30:11 GMT)
--------------------------------------------------

In molecules, carbon atoms connected to four different groups rotate plane polarized light rightward or leftward by a certain number of degrees. To come up with a definite property, a certain path length is usesd with w certain concentration. The D stands for light emitted by a sodium atom (one particular wavelength).

--------------------------------------------------
Note added at 10 mins (2007-07-07 17:31:47 GMT)
--------------------------------------------------

Molecules having this property are known as "chiral molecules" (i.e. molecules with a handedness. Similar to a screw, can be left handed right handed.

--------------------------------------------------
Note added at 11 mins (2007-07-07 17:33:04 GMT)
--------------------------------------------------

http://cns.uni.edu/~macmilla/mcmurry/mcmurry_chapter_9/sld01...

--------------------------------------------------
Note added at 12 mins (2007-07-07 17:33:44 GMT)
--------------------------------------------------

The specific rotation is represented by the formula
100α
[α]xt = ,
l c
where t = the temperature of measurement,
x = the wavelength or the name of the specific monochromatic light
of spectrum used (when D line is used, indicate as D),
α = the angle, in degrees, of the rotation of plane of the polarized
light,
l = the thickness of the layer of the measured solution, i.e., the
length of the polarimeter tube (mm),
c = the number of grams of a sample in 1 ml of the solution.
Hereinafter in the Monographs, such a specification as “[α]20D = +20.5 -
+21.5 ゚(1 g, freshly boiled and cooled water, 10 ml, on the dried basis)”indicates
that the specific rotation of the substance is +20.5 - +21.5 ゚, when determined on
the dried basis for the solution which is prepared by weighing accurately about 1 g of
the test substance and dissolving in newly boiled and cooled water to make exactly 10
ml.

--------------------------------------------------
Note added at 13 mins (2007-07-07 17:34:10 GMT)
--------------------------------------------------

You might also say "optical specific rotation".

--------------------------------------------------
Note added at 16 mins (2007-07-07 17:37:41 GMT)
--------------------------------------------------

Between optical specific rotation and specific rotation, the latter (specific rotation) is better.

** specific rotation **
The ** specific rotation ** of a chemical compound [α] is defined as the observed angle of optical rotation α 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:

Sucrose +66.47°
cholesterol −31.5°
Camphor +44.26°
Penicillin V +223°
taxol −49°

--------------------------------------------------
Note added at 18 mins (2007-07-07 17:39:18 GMT)
--------------------------------------------------

Why ** specific rotation ** and not simply ** rotation **?

------------------------------------------------------------------------

he specific rotation can only be used to characterize compounds that are
chiral - those that can exist as a pair of enantiomers - two compounds
with structures that are related as nonsuperimposable object and mirror
image. Chiral substances are the only type of substances that exhibit
optical activity. The presence of optical activity shows that the
substance is chiral. In fact the specific rotation is used to
characterize each individual enantiomer.

There seems to be another aspect to the question: Why the specific
roation rather than another value for the rotation? The specific
rotation is used because it is the rotation that would be obtained under
a "standardized" set of conditions. In this way the specific rotation of
one compound can be compared to that of another without concern for
whether they were obtained unde that same set of conditiond. While the
sign of the rotation for a compound does not change with conditions, the
numerical value changes with changes in condition.

The ** specific rotation ** represents the value of the rotation one would
obtain when the pathlength is one decimeter and the concentration of the
substance in a solvent is 1.00 g of substance per mL of solvent. The
specific rotation is also specific for a given temperature and a given
wavelenght of light.
Selected response from:

Zareh Darakjian Ph.D.
United States
Local time: 12:48
Grading comment
Thanks to Zareh and all who agreed. Zareh, I really appreciate your in-depth explanations - I do remember chiral molecules from college chemistry, but it had been a while. This is just the sort of information a translator needs to understand not just the words, but also the concepts. Too bad I can award only 4 points maximum!
4 KudoZ points were awarded for this answer

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Summary of answers provided
5 +4specific rotationZareh Darakjian Ph.D.


Discussion entries: 1





  

Answers


7 mins   confidence: Answerer confidence 5/5 peer agreement (net): +4
specific rotation


Explanation:
This is the rotation caused by chiral molecules


--------------------------------------------------
Note added at 9 mins (2007-07-07 17:30:11 GMT)
--------------------------------------------------

In molecules, carbon atoms connected to four different groups rotate plane polarized light rightward or leftward by a certain number of degrees. To come up with a definite property, a certain path length is usesd with w certain concentration. The D stands for light emitted by a sodium atom (one particular wavelength).

--------------------------------------------------
Note added at 10 mins (2007-07-07 17:31:47 GMT)
--------------------------------------------------

Molecules having this property are known as "chiral molecules" (i.e. molecules with a handedness. Similar to a screw, can be left handed right handed.

--------------------------------------------------
Note added at 11 mins (2007-07-07 17:33:04 GMT)
--------------------------------------------------

http://cns.uni.edu/~macmilla/mcmurry/mcmurry_chapter_9/sld01...

--------------------------------------------------
Note added at 12 mins (2007-07-07 17:33:44 GMT)
--------------------------------------------------

The specific rotation is represented by the formula
100α
[α]xt = ,
l c
where t = the temperature of measurement,
x = the wavelength or the name of the specific monochromatic light
of spectrum used (when D line is used, indicate as D),
α = the angle, in degrees, of the rotation of plane of the polarized
light,
l = the thickness of the layer of the measured solution, i.e., the
length of the polarimeter tube (mm),
c = the number of grams of a sample in 1 ml of the solution.
Hereinafter in the Monographs, such a specification as “[α]20D = +20.5 -
+21.5 ゚(1 g, freshly boiled and cooled water, 10 ml, on the dried basis)”indicates
that the specific rotation of the substance is +20.5 - +21.5 ゚, when determined on
the dried basis for the solution which is prepared by weighing accurately about 1 g of
the test substance and dissolving in newly boiled and cooled water to make exactly 10
ml.

--------------------------------------------------
Note added at 13 mins (2007-07-07 17:34:10 GMT)
--------------------------------------------------

You might also say "optical specific rotation".

--------------------------------------------------
Note added at 16 mins (2007-07-07 17:37:41 GMT)
--------------------------------------------------

Between optical specific rotation and specific rotation, the latter (specific rotation) is better.

** specific rotation **
The ** specific rotation ** of a chemical compound [α] is defined as the observed angle of optical rotation α 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:

Sucrose +66.47°
cholesterol −31.5°
Camphor +44.26°
Penicillin V +223°
taxol −49°

--------------------------------------------------
Note added at 18 mins (2007-07-07 17:39:18 GMT)
--------------------------------------------------

Why ** specific rotation ** and not simply ** rotation **?

------------------------------------------------------------------------

he specific rotation can only be used to characterize compounds that are
chiral - those that can exist as a pair of enantiomers - two compounds
with structures that are related as nonsuperimposable object and mirror
image. Chiral substances are the only type of substances that exhibit
optical activity. The presence of optical activity shows that the
substance is chiral. In fact the specific rotation is used to
characterize each individual enantiomer.

There seems to be another aspect to the question: Why the specific
roation rather than another value for the rotation? The specific
rotation is used because it is the rotation that would be obtained under
a "standardized" set of conditions. In this way the specific rotation of
one compound can be compared to that of another without concern for
whether they were obtained unde that same set of conditiond. While the
sign of the rotation for a compound does not change with conditions, the
numerical value changes with changes in condition.

The ** specific rotation ** represents the value of the rotation one would
obtain when the pathlength is one decimeter and the concentration of the
substance in a solvent is 1.00 g of substance per mL of solvent. The
specific rotation is also specific for a given temperature and a given
wavelenght of light.

Zareh Darakjian Ph.D.
United States
Local time: 12:48
Specializes in field
Native speaker of: Native in EnglishEnglish, Native in ArmenianArmenian
PRO pts in category: 63
Grading comment
Thanks to Zareh and all who agreed. Zareh, I really appreciate your in-depth explanations - I do remember chiral molecules from college chemistry, but it had been a while. This is just the sort of information a translator needs to understand not just the words, but also the concepts. Too bad I can award only 4 points maximum!

Peer comments on this answer (and responses from the answerer)
agree  texjax DDS PhD: WOW! I really needed to brush up on my chemistry, thanks Zareh!
15 mins
  -> Thank you, Doctor!

agree  Giovanni Pizzati
15 mins
  -> Thank you, Giovanni!

agree  Vepalm: Good.
40 mins
  -> Thank you, Vepalm! I appreciate your expert opinion.

agree  Antonia Toth
19 hrs
  -> Thank you, Antonia for your expert "agree"!
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