Questions tagged [optical-properties]
Questions related to color as well as the reflecting and refracting properties of chemicals.
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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 ...
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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 ...
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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) ...
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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 ...
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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 ...
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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 ...
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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 ...
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Relating the diffraction angle to the angle from the “zeroth order beam”
What I’ve been asked relates to diffraction from scattering atoms in materials with periodic atom array structures.
“For two scattered in a beam of radiation that are a distance d apart, show that the ...
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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-...
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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 ...
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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 ...
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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....
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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 ...
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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 ...
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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 ...
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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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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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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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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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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?
user102687
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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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