Skip to main content

Questions tagged [optical-properties]

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

Filter by
Sorted by
Tagged with
-1 votes
1 answer
90 views

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 ...
-1 votes
1 answer
60 views

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 ...
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 ...
1 vote
0 answers
12 views

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 ...
8 votes
1 answer
460 views

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 ...
0 votes
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 ...
1 vote
1 answer
28 views

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 ...
0 votes
0 answers
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 ...
3 votes
0 answers
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 ...
1 vote
0 answers
27 views

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 ...
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) ...
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 ...
3 votes
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 ...
2 votes
1 answer
119 views

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 ...
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....
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 ...
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-...
7 votes
0 answers
48 views

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 ...
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 ...
18 votes
6 answers
10k 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 $\pu{700 nm});$ ...
0 votes
0 answers
126 views

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 ...
-1 votes
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 ...
2 votes
1 answer
623 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 ...
3 votes
1 answer
196 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 ...
1 vote
1 answer
260 views

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, ...
1 vote
0 answers
28 views

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 ...
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 (...
2 votes
1 answer
838 views

How many stereoisomers can exist for 4,5-bis(3-hydroxyoct-1-en-1-yl)cyclopentane-1,3-diol?

Q.10 For the given compound $\ce{X}$, the total number of optically active stereoisomers is ____. This is from JEE Advanced 2018 second question paper. I thought the answer to be at least 32 because ...
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 ...
4 votes
1 answer
320 views

Approximate magnetic susceptibility of these liquid propellants?

This question asks if the comparatively large paramagnetic susceptibility of liquid oxygen (LOX) is considered when designing rocket tank and engine systems. This comment suggests fuels such as RP-1 (...
1 vote
1 answer
6k views

What is the color of elemental silver?

From my lab book it says it is black? I don't understand how we know the color of it is black. Can anyone explain?
7 votes
1 answer
2k views

Home science optical absorption test for approximate caffeine quantity in coffee?

I started with How can you measure the caffeine content of a liquid at home? in the cooking stackexchange, but the test strips were only qualitative (yes/no) and don't seem to exist anymore, and the ...
2 votes
2 answers
2k views

Is the refractive index of a solution of four substances the median of the four substances' refractive index?

I need to determine the purity of a solution and we need to discuss about the 'theoretical' refractive index of the substance that we are supposed to have.
0 votes
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 ...
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 ...
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 ...
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-...
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?
16 votes
1 answer
2k views

How are polarizabilities measured experimentally?

Most common spectroscopies that produce either a full spectrum, a tensor, or a scalar value have a specific instrument associated with them that is relatively self-contained and not custom. For ...
0 votes
1 answer
2k views

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, ...
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 ...
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 ...
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)}\...
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 ...
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 ...
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 ...
-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 ...
4 votes
2 answers
820 views

Can a system of 2 consecutive biphenyl systems be optically active , even if any adjacent biphenyl systems aren't optically active?

This question came in an online test, where they asked whether or not 22,26-dibromo-12,32-dichloro-23,25-diiodo-16,36-dimethyl-11,21:24,31-terphenyl was optically active. The answer is that, it is ...
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?
10 votes
1 answer
356 views

Optical activity of starch

In this German Wikipedia article about optical activity, I found the beautiful picture of starch granules: Unfortunately, I have no idea what I am looking at. What are these crosses and why are they ...