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Questions tagged [optical-properties]

Questions related to color as well as the reflecting and refracting properties of chemicals.

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What is the lowest possible refractive index a solid can have?

In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium. What is the minimum ...
Nitrogen-8's user avatar
-1 votes
1 answer
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How exactly are mirror images of molecules rotated to determine enantiomeric pair?

I know there are many similar questions to this but none could clear my confusion over how exactly the mirrored molecules is rotated i.e on which axis it is rotated to superpose with the original ...
ADITYA DAS's user avatar
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DIY hydrolysis of starch with copper and test them with polarizer sheet due to muta rotation

When I read about muta rotation — the interconversion of alpha to beta glucose — recently, I decided to do it with rice, because rice contain 66% of starch which is alpha glucose polymer. To hydrolyze ...
karthik keyan smk's user avatar
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0 answers
23 views

Finding or designing a thermochromic that becomes transparent to NIR at room temperature

Are there known nanoparticles or organic materials that have the following properties: absorb near-infrared light and convert them to heat at temperatures below a certain threshold become mostly ...
Heye's user avatar
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1 answer
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Co(NO3)2 forming colloid in H2O, and Methanol

I was just trying to make a stock solution of some Co(NO3)2 . One in H2O, another in Methanol. Both don't completely dissolve. They're almost dissolved and appear near translucent but when shining a ...
Ahmer Imam's user avatar
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54 views

When C2 axis of symmetry is present then is the compound meso?

If suppose a compound has C2 axis of symmetry then is it confirmed that the compound will be meso or it can have an enantiomeric pair? And which of following conditions are sufficient enough to ...
Garv Chaudha's user avatar
3 votes
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37 views

Detection of contamination from salicylic acid via either single excitation fluorometer or via absorbance

My colleague detected fluorescent contamination likely from salicylic acid in some water samples. I have made a new batch and want to check whether my new samples also have this contamination. 1. Can ...
claire's user avatar
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What is the diffusivity of colloidal Formazine in water?

I have synthesized Foramzine in an aqueous solution (turbidity = 4000 NTU), and will be further diluting it. I would like to know the diffusion coefficient (diffusivity/mass diffusivity) of colloidal ...
optomechanic's user avatar
5 votes
1 answer
92 views

Biocompatible, high refractive index medium for 780 nm?

I am trying to find a medium for optics experiments on living cells. I have been using yeast cells, saccharomyces cerevisiae and saccharomyces boulardii, and need a medium with refractive index (RI) ...
Isabela Sousa's user avatar
1 vote
1 answer
210 views

Doubt in chirality and pseudo chirality

So a carbon atom is chiral if it has 4 different group attached to it, and it is pseudo chiral if it has 3 different groups of atoms attached to it, where the 2 similar groups have different ...
Ham Lemon's user avatar
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1 answer
148 views

Application of Beer-Lambert Law to Absorptivity

The Beer-Lambert law gives a linear relationship between the concentration of a solute $c$ and the absorbance $A$, with absorbance defined as the logarithm of the ratio between the transmitted radiant ...
Jonathan Huang's user avatar
2 votes
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Which gas at 15 °C and 1 atmosphere of pressure has the highest refractive index in visible light?

For my own curiosity's sake, I am attempting to find the gas that at 15 °C and 1 atmosphere of pressure in pure form has the highest refractive index on average and overall, for visible light. Assume ...
ProfessorMoreRight's user avatar
2 votes
2 answers
469 views

How can I determine a stereogenic centre?

I have a problem understanding stereogenic centres. A stereogenic centre is specified (in the case of organic chemistry that I am interested to) as a carbon atom which is bounded to four different ...
Kani Pen's user avatar
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2 votes
1 answer
52 views

Diffraction Derivation- relating the angle between deflected ray and original

This relates to diffraction from objects with a periodic structure. I’m trying to relate the psi angle (diffracted angle) to the theta angle (angle between diffracted ray and the original non-...
Aurora's user avatar
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7 votes
0 answers
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Why all commercial SPR instruments use angular interrogation?

Surface plasmonic resonance biosensor devices are used to measure analyte concentration, kinetics, affinity, and specificity without any need for labels. This technique involves the bonding of the ...
C.X.F.'s user avatar
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11 votes
1 answer
3k views

Difference between a "cartoon" flame test and a "real" flame test? How do chemists do flame tests correctly?

This well-received answer to Why does the same electron transition release photons of different frequencies for some elements? begins with the following intriguing passage: I am glad that you updated ...
uhoh's user avatar
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7 votes
1 answer
330 views

How exactly thermal infrared (e.g. FLIR) cameras image methane leaks? Are they measuring a temperature difference or an emissivity difference or...?

The story Infrared camera shows the impact of vehicle emissions says: In an effort to visually demonstrate the potentially fatal impacts of air pollution, FLIR Systems (Wilsonville, OR, USA; www.flir....
uhoh's user avatar
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When does the angle between the planes in tetrahedral molecule with central atom deviate from 90°?

Consider an atom X bonded to four other atoms A, B, C, D in a tetrahedral fashion with sp³ hybridisation. If A, B, C, D are the same, every bond angle is 109.47°, and the angle between the planes ...
Ritil's user avatar
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1 answer
298 views

Does no optical rotation always implies optical inactivity? [duplicate]

This question popped up in my mind in reference to this question, Is a compound optically active if plane polarised light is deflected by an angle of n*(2π) angles? Suppose that I give a chemistry ...
Ritil's user avatar
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2 votes
1 answer
624 views

How does Entropy influence the racemization of an optically active compound?

We were doing the topic "Isomerism" in our Organic Chem class and there's a question in our worksheet whose answer I haven't really understood, the question is as follows: The racemization ...
Aaryan's user avatar
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1 answer
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Why is instant coffee powder not as dark as the coffee resulting from it?

Instant coffee granules generally are of a light brown colour, while coffee made from it is a deep black. Pigments are far more concentrated in the dry form, to add water is to dilute them. Still, ...
HannesH's user avatar
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0 answers
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Is there a stretchable, transparent polymer like PDMS, but not so hydrophobic?

I'm looking for something like PDMS, but not as hydrophobic. I'm trying to form 2d crystals using the surface tension of an evaporating droplet to organize microspheres into an ordered array. PDMS ...
Thomas's user avatar
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1 vote
1 answer
168 views

How to identify an error in cut off filter (optical) usage when running spectrophotometry?

In spectrophotometry, often a cut off optical filter is used. With reference to a long-pass filter, which rejects any wavelengths outside a predetermined interval: low transmission in short ...
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3 votes
1 answer
197 views

Do lithium iron phosphate cathodes change color during charging and discharging while losing lithium ions?

The following reaction takes place in a lithium iron phosphate (LFP) battery: $$\ce{LiFePO4 -> FePO4 + Li+ + e-}.$$ According to Wikipedia, $\ce{LiFePO4}$ is a grey, reddish grey, brown, or black ...
bryan dunn's user avatar
4 votes
1 answer
419 views

Does syn-dihydroxylation form racemic mixture?

I have been asked to determine the nature of the product for the following reaction: And as I recognized this reaction to be a case of syn-dihydroxylation, my obvious response was that the product ...
Aniruddha's user avatar
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3 votes
0 answers
71 views

Does optical isomerism fall under the category of stereoisomerism?

I have been asked to find the total number of dichlorination products (including stereoisomers) for the following reaction: I have figured out nine possible structures out of which two are optically ...
Aniruddha's user avatar
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0 answers
1k views

What are the limitations of the D, L system and the (+), (-) system for naming organic compounds

In organic chemistry, both the D, L system and the (+), (-) system are widely used, in conjunction with the modern (R, S) system. The D, L system names an organic molecule based on the direction that ...
seamos's user avatar
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8 votes
1 answer
6k views

Why are complexes of type MA3B3 not optical active?

Complexes of type $\ce{MA3B3}$ have two geometrical isomers, namely: fac-isomer mer-isomer If we look closely at the mer-isomer, it has a plane of symmetry, so it is optically inactive. But the fac-...
Harsh's user avatar
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3 votes
2 answers
195 views

Chirality and Optical activity

Do all chiral objects rotate the plane of polarization of EM waves? For example my hand is chiral, will it rotate the plane of polarization of EM waves of suitable wavelength?
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1 answer
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Which are the Geometrical isomers of the complex [Cr(NH3)2Cl2(en)]+?Is it one or two?

I was recently studying coordination compounds and i came across optical isomerism shown by complexes.I think that the complex i gave above have 4 geometrical isomers(I think this is where I am wrong, ...
Muhammed Rishan's user avatar
1 vote
1 answer
655 views

Are all 'dextrorotatory' sugars in biology actually 'd' or '+' in chirality?

When papers or articles say that all proteinogenic amino acids are 'levorotatory' or 'L', they often make a point of saying that only half of them are truly, optically levorotatory. All of them (...
Kurt Hikes's user avatar
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1 vote
0 answers
90 views

How to calculate the refractive index of mixtures? [duplicate]

In "How to Calculate the Refractive Index of a Formulation", the article outlines a method to find the refractive index of a mixture but the sources don't lead to any evidence regarding its ...
Adarsh Payyavula's user avatar
1 vote
0 answers
46 views

Beer-Lambert law absorption by each species

Light travels length $l$ through a medium with $n$ independently absorbing species with extinction coefficients $\alpha_1,\dots,\alpha_n$. According to Beer-Lambert law, the amount of light absorbed ...
arax's user avatar
  • 111
4 votes
2 answers
746 views

Can a chiral molecule be optically inactive?

Does there exist a chiral compound with zero optical activity? It seems possible that for some (chiral) arrangement of atoms, the optical activity of one section of the molecule could be exactly ...
user avatar
0 votes
1 answer
1k views

Kinetics of inversion of cane sugar

Question 1 The formula for concentration of cane sugar as a function of time is given by $$k = \left(\frac{2.303}{t}\right) \log\left[\frac{\alpha(0) - \alpha(\infty)}{\alpha(t) - \alpha(\infty)}\...
Manit Agarwal's user avatar
0 votes
0 answers
90 views

What is the meaning of pi selectivity?

I came across this term while going through a research paper for the first time of organic chemistry on diastereoselectivity of tricyclo[2.1.0.02,5]pentan-3-ones. I am not familiar with the term and ...
Nyx_Valatoria's user avatar
10 votes
1 answer
2k views

How is plane polarized light rotated by chiral compounds? [duplicate]

There are plenty of questions related to this topic on this site but no proper answer. Can anyone please explain to me how plane polarized light is rotated by chiral compounds, and why it cannot be ...
Manas's user avatar
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1 vote
0 answers
56 views

How to predict which type of optical isomerism [closed]

When I learnt about optical activity in school, my teacher told me that there is no way to theoritically predict whether a compound is dextrorotatory or leuvorotatory. How is that possible?
ICHO aspirant's user avatar
-2 votes
2 answers
2k views

In the reaction mentioned what percentage of reaction proceeds via SN1 mechanism?

2-iodo butane (having radioactive iodine) reacts with KI (having non radioactive iodine). Rate of loss of optical activity was 1.96 times the rate of loss of radioactivity. What percentage of reaction ...
sfumato's user avatar
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-2 votes
1 answer
137 views

Optical activity of substituted biphenyl [closed]

How come the given compound in the diagram is optically inactive? The two rings should be in different planes due to steric hindrance between $\ce{COOH}$ and bromine. How am I wrong?
Loveforphysics's user avatar
0 votes
0 answers
28 views

How can randomly oriented molecules in a liquid solution create a certain polarization pattern (d or l)? [duplicate]

How can a large number of moving, randomly-oriented chiral molecules in a watery solution twist light only to the left or only to the right? Wouldn't a levorotary molecule become dextrorotary if I ...
Kurt Hikes's user avatar
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0 votes
1 answer
102 views

How is 1,4,6-trichlorodiamantane optically inactive? [closed]

How this compound is optically inactive I can't analyse any element of symmetry in this compound.
Vijay Sharma's user avatar
0 votes
0 answers
520 views

Are centre of symmetry(COS) and alternate axis of symmetry(AAOS) dependent on each other?

COS=Centre of symmetery AAOS=Alternate axis of symmetry Lets suppose a molecule has a COS. Does it need to have AAOS? What about the converse? If a molecule has AAOS does it necessarily have a COS? ...
PRITIPRIYA DASBEHERA's user avatar
12 votes
2 answers
779 views

What is the difference between quantities reported as optical rotation and circular birefringence?

Optical activity gets complicated quickly and the following question is intended to avoid threshold confusion. The linked lecture note* seems very accessible to me and Table 10.6 in particular is ...
daniel's user avatar
  • 984
6 votes
1 answer
144 views

Question about a line from Rosenfeld's paper on optical rotation

There are a lot of papers on optical rotation which cite Rosenfeld's (German) 1928 paper "Quantum mechanical theory of natural optical rotation..." [Quantenmechanische Theorie der naturlichen ...
daniel's user avatar
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-3 votes
1 answer
420 views

Optical activity checking

In the following cyclopentane deratives, why can't I say that a,b,e have a center of symmetry so they are optically inactive and c as it has a plane of symmetry as shown is also optically inactive? ...
Equation_Charmer's user avatar
2 votes
1 answer
284 views

The number of optical isomers of 3,4-dichlorobutan-2-ol

The number of optical isomers possible for the given organic molecule is? $\ce{CH_3-C^*H(OH)-CHCl-CH_2Cl}$ (the configuration is fixed at $\ce{C^*}$) The given answer is 2. The carbon marked with an ...
Tapi's user avatar
  • 315
-1 votes
1 answer
216 views

Optical activity of cis-trans isomers of a co-ordination compound [closed]

Why do geometrical (cis and trans) isomers of [Pt(NH3)(Br)(Cl)(py)] not show optical activity ? Thanks In Advance...
user74156's user avatar
1 vote
1 answer
623 views

Is specific rotation defined for mixtures of enantiomers or meso compounds?

I recently had to do an experiment where we had to make a racemic mixture of D and L complexes and then resolve the enantiomers, and measure the optical rotation of the racemic mixture, and the ...
S R Maiti's user avatar
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2 votes
0 answers
90 views

Why upon melting of PEO between crossed polars colours appear?

Crystalline PEO when under crossed polars shows distinct Maltese cross pattern. Being birefringent, when polymer crystal align with the polarizer or analyser it shows extinction regions (effect known ...
Wojtek Adamczyk's user avatar