Questions tagged [optical-properties]

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

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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, ...
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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 ...
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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
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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 ...
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4 votes
1 answer
108 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 ...
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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 ...
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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 ...
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8 votes
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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-...
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3 votes
2 answers
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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, ...
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1 answer
202 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 (...
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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 ...
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1 vote
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33 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 ...
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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 ...
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1 answer
378 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)}\...
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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 ...
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10 votes
1 answer
998 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 ...
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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?
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-2 votes
2 answers
838 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 ...
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-2 votes
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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?
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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 ...
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-1 votes
1 answer
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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.
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177 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? ...
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12 votes
2 answers
576 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 ...
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6 votes
1 answer
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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 ...
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1 answer
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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? ...
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2 votes
1 answer
251 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 ...
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1 answer
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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...
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1 vote
1 answer
363 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 ...
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2 votes
0 answers
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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 ...
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0 votes
1 answer
165 views

Which of the following isomers of 2,3‐dihydroxy‐4‐methoxy‐4‐oxobutanoic acid are identical?

Which of the following are identical? A and B are identical A and B are diastereomers A and C are enantiomers A and B are enantiomers What I know is that when we rotate a Fisher projection by 180°, ...
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3 votes
0 answers
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What gas would be suited best to form a density gradient in a long tube? [closed]

I want to set up an aero-optics experiment using a sealed ~5 m length of pipe with a gas inside. The gas must form a density gradient, and must be transparent enough to view a target at the other end ...
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1 vote
1 answer
43 views

When to permute two times to find optical configuration [closed]

I'm learning about S and R configuration, and I know that in case where the 4th substituant is not behind we should permute it with the one which is behind. then we find the new configuration and use ...
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17 votes
5 answers
8k views

Is there a commercial liquid with refractive index greater than two?

I need a commercially available liquid with the following properties: refractive index $n > 2$ at room temperature $(T \approx\pu{23 °C});$ transparent in visible region $(380$ to $\pu{700 nm});$ ...
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1 vote
1 answer
825 views

Conditions for molecular dissymmetry

In my textbook, under the topic "Asymmetric and Dissymmetric Compounds", the following statement is given: A molecule which does not possess plane of symmetry, centre of symmetry, and alternating ...
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2 votes
1 answer
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Is methanol optically active?

Strictly on theoretical basis, not based on experimental results. I can very well be wrong, but I think that methanol should be optically inactive because it has a plane of symmetry passing through ...
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0 votes
2 answers
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Optical activity of (1r,3R,5S)-3,5-dimethyl-4-methylidenecyclohexan-1-ol

Could anyone explain why compound L is not optically active?
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2 votes
1 answer
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Is there a relationship between loss of electrons and EM wave reflection? [closed]

Is there a relationship between the loss of electrons in a cation and the amount of electromagnetic spectrum, a compound of this cation would subsequently reflect or transmit? For example, any ...
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4 votes
0 answers
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What would superionic water ice look like?

Phys.org's Giant lasers crystallize water with shockwaves, revealing the atomic structure of superionic ice links to Nature Physics: Experimental evidence for superionic water ice using shock ...
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2 votes
1 answer
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How to detect nM levels of Copper(I) Oxide in blood?

I'm trying to design an experiment to detect nM quantities of Copper(I) Oxide in fish blood. Are there any specific tests for Copper(I) Oxide that can be used to detect trace quantities(~nM)? Any non-...
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3 votes
0 answers
48 views

A formula for the refractive index of a gas dependent on temperature and pressure

I am in search for a formula that gives me the refractive index of a gas at a given temperature and pressure. Does such a formula exist? Ideally the solution should have this form: $n_g(t, p) = \...
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3 votes
1 answer
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Would Z and E isomers show different optical activity?

Consider this compound, which is in E-configuration and that red asterisk denotes the chiral carbon. If I were to somehow cause the E-configuration of the alkene part to Z-configuration keeping the ...
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2 votes
1 answer
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Synthetic ruby - damaged by heat less than its melting point?

A bit of a jewellery question but chemistry related. I want to encase a synthetic ruby (corundum, Al2O3) in silver by melting the silver around it. Either in a furnace or by casting. The MP of silver ...
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1 vote
1 answer
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Optical activity [closed]

I was studying about the optical activity of compounds. And I found , it is written that the chirality of a molecule is the necessary and sufficient condition for a molecule to be optically active. I ...
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-1 votes
2 answers
2k views

Can we rotate a mirror image by any angle to check if it is superimposable? [closed]

A molecule is chiral when it is different from its mirror image, and achiral if it is identical to its mirror image. To check if the mirror image is identical to the original object, we have to check ...
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1 vote
1 answer
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What is the refractive index of poly(methacrylamide)?

I've been looking for the index of refraction for poly(methacrylamide). I searched several vendors and in https://polymerdatabase.com/ with no success. Is there any database where I can find this ...
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3 votes
0 answers
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How to align povidone-iodine molecules in order to look for optical polarization

In this answer I mention how early polarizing filters (e.g. sunglasses) were made by doping a polymer with iodine atoms and then stretching the film to orient the polymer molecules. Electrons donated ...
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6 votes
0 answers
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What compound has the strongest optical rotation of polarised light?

A question recently asked here whether compounds know to be chiral can have non-measurable optical rotations: Are there chiral compounds that don't rotate plane-polarized light?. Apparently they ...
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11 votes
1 answer
1k views

Are there chiral compounds that don't rotate plane-polarized light?

I know that meso compounds have chiral centers but don't rotate plane-polarized light, and I know that there can be non-traditionally chiral compounds (e.g. ones with large substituents that prohibit ...
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5 votes
3 answers
505 views

Can two lone pairs in different orbitals make a chiral centre?

Is it possible that if the two lone pairs in a molecule occupy different orbitals, then could this make the molecule chiral? What I mean is, suppose a carbon atom is attached to two different atoms ...
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