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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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36 votes
3 answers
7k views

A compound that absorbs all visible light

Is there a compound that absorbs all visible light?
oushida 's user avatar
31 votes
3 answers
13k views

Are there non-transparent gases?

Are there gases that are not transparent at room temperature (i.e. at temperature below the point where the substance starts to radiate visible light due to heating)?
Anixx's user avatar
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28 votes
2 answers
3k views

Why are there no cheap diamond equivalents?

We recently learned in school that diamonds sparkle as the are very optically dense, meaning that it takes longer for light to pass through them, thus meaning that the light totally internally ...
Deep's user avatar
  • 511
22 votes
1 answer
2k views

Are there any known chemical properties of tritium water that make it unusually different from protium water?

I suppose the first question supporting the main question is, has tritium water ever been synthesized in sufficient quantity to test chemical properties? If so, and apart from the obvious radioactive ...
docscience's user avatar
  • 2,773
21 votes
1 answer
2k views

How to think of solvated electrons?

This excellent answer explains at length what's happening in this fascinating video entitled Liquid Electrons - Periodic Table of Videos. In the screenshot below, the metallic-looking solvated ...
uhoh's user avatar
  • 5,888
20 votes
0 answers
3k views

Why is nitrogen dioxide (NO2) brown? [closed]

I don't understand why nitrogen dioxide $\ce{NO2}$ is coloured brown when nitrate $\ce{NO2-}$ and dinitrogen tetroxide $\ce{N2O4}$ are not. I understand it is due to absorption of light when its ...
saatwik upadhyay's user avatar
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 $\pu{700 nm});$ ...
Persian_Gulf's user avatar
17 votes
2 answers
293 views

Rock that transfers image

This is a question that has been bugging me for over 15 years! In high school while studying elements our teacher showed us a clear white rock or element. It was simply flat on both sides but when ...
Frank's user avatar
  • 459
16 votes
1 answer
2k views

What is happening in this video of solvated electrons donated from sodium in ammonia?

I just saw the Periodic Video Liquid Electrons - Periodic Table of Videos where sodium is added to liquid ammonia. The demonstration shows that even if electrons are solvated, if you have a high ...
uhoh's user avatar
  • 5,888
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 ...
pentavalentcarbon's user avatar
14 votes
1 answer
8k views

Maximum observed optical rotation through a polarimeter

Is there a maximum optical rotation of plane polarized light that can be observed using a polarimeter? I understand that in a polarimeter, light passes through a filter that converts it into plane ...
tkhanna42's user avatar
  • 2,545
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
12 votes
1 answer
1k views

How is polarization of light measured?

Chiral molecules are classified as dextrorotatory (+) or levorotatory (-) depending on whether they rotate plane-polarized light (ppl) to the right or left. My question is, how is such a measurement ...
Steven's user avatar
  • 149
11 votes
1 answer
2k 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 ...
Carl Schildkraut's user avatar
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
  • 5,888
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
  • 177
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 ...
waterlemon's user avatar
  • 1,651
9 votes
1 answer
3k views

Does mercury fulminate really look like crystal methamphetamine?

In the AMC series Breaking Bad , Walter (aka Heisenberg) smuggles in a bag of mercury fulminate under the guise of crystal methamphetamine and threatens to blow the room up if he doesn't get his money....
docscience's user avatar
  • 2,773
9 votes
2 answers
14k views

Why do only chiral molecules rotate the plane of polarized light and how do they rotate it?

I have learnt that only chiral or unsymmetrical molecules can rotate the plane of linearly polarized light. But, why is it so? And how can molecules rotate the plane or what does it actually mean by ...
Rajath Radhakrishnan's user avatar
8 votes
2 answers
3k views

Does inversion of configuration necessitate reversed optical rotation?

Say, optically pure 2-bromobutane undergoes $\mathrm{S_N2}$ reaction with an alkali to form 2-butanol. The configuration about chiral carbon will now be inverted, but is it necessary that the sign of ...
Abhishek's user avatar
  • 365
8 votes
1 answer
7k views

What are chiral environments?

I keep seeing the term cropping up, but cannot seem to find a definition for it. My understanding is that it is an environment in which, when the isomers interact with the environment, the two ...
Meep's user avatar
  • 1,697
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
  • 111
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 ...
uhoh's user avatar
  • 5,888
8 votes
2 answers
372 views

Is there a liquid crystal or similar material that gets cloudy when an electric field is applied, but is otherwise clear?

Is there a way to make a liquid, such as a liquid crystal material, transition from cloudy or clear and vice-versa using only electric current? By cloudy, I mean, similar to the effect that ...
Hunter Beast's user avatar
8 votes
1 answer
506 views

Discovery of optical activity of enantiomers - where did the idea of using polarized light came from?

According to Wikipedia, optical activity was first observed in 1811 in quartz. Louis Pasteur's contribution is also mentioned there and in other sources as a major advancement in establishing optical ...
Don_S's user avatar
  • 1,410
7 votes
1 answer
2k views

What is there in this 3D representation of organic molecules I fail to grasp?

I think there's a basic idea I'm missing about 3 Dimensional representation of molecules. I think it may be about converting to Fischer representation. Consider the following two products of ...
Shubham's user avatar
  • 217
7 votes
2 answers
1k views

Why do shape and size have the greatest effect on the optical properties of nanoparticles?

The LSPR properties of nanoparticles depend on a number of factors, including shape, size, material, crystal structure, dielectric environment, etc. However, it has been consistently shown that shape ...
jojoma42's user avatar
7 votes
1 answer
2k views

What salts are/are not birefringent?

Is there a quick way to determine if a salt (or ionic compound in general) crystal should be birefringent from its formula without having to know/look up the crystal structure? When I'm looking for ...
Nick T's user avatar
  • 2,563
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
  • 5,888
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 ...
uhoh's user avatar
  • 5,888
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 ...
C.X.F.'s user avatar
  • 1,859
7 votes
0 answers
370 views

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 ...
matt_black's user avatar
6 votes
2 answers
972 views

Effect of direct exposure to sunlight on various drugs

Today, we were discussing optical activity in class and our teacher said that some drugs are kept in dark coloured bottles to avoid direct exposure to sunlight. Same is the case with some other drugs ...
anamika Singh's user avatar
6 votes
2 answers
16k views

Is tetraammine dichloro cobalt (III) an optically active compound?

Is $$ \text{Co}[{(\text{N}{\text{H}}_{3})}_{4}{\text{Cl}}_{2}]$$ optically active? If so, write its stereo-isomers. I know that for a compound to be optically active, it should rotate the plane of ...
Henry's user avatar
  • 443
6 votes
1 answer
2k views

Are a meso compound and its mirror image isomers?

How are meso isomers even isomers? By definition, meso isomers are compounds that are superposable on their mirror images, but doesn't that mean that the mirror image is just the same compound? Can ...
Mahathi Vempati's user avatar
6 votes
1 answer
8k views

Why are square planar coordination compounds with four different ligands optically inactive?

Why do square planar coordination compounds of type $\ce{[Mabcd]}$ not show optical activity, although they contain 4 different ligands (i.e. chiral central metal atom)?
Nikhil Chandratre's user avatar
6 votes
1 answer
495 views

D-Threose: reduction and optical activity

I've bumped into this exercise: Judging by the mechanism of reaction between D-threose and $\ce{NaBH4}$, do you think the final product will be optically active? To me looks like a reduction, ...
Riccardo Gee's user avatar
6 votes
1 answer
5k views

Why does zinc sulfide glow?

Zinc sulfide is used in road signs because when light from cars hit the road signs, it glows. What actually is the reason for the glowing of road signs (actually glowing of $\ce{ZnS}$)?
Nilay Ghosh's user avatar
  • 26.3k
6 votes
2 answers
8k views

UV-Transparent Plastic?

I am looking for a type of plastic, preferably in the form of a sheet or film, that is weatherproof, durable, flexible, and both transparent and UV-transparent. Most films I've seen so far are treated ...
Joseph's user avatar
  • 61
6 votes
1 answer
1k views

A compound that only absorbs UV-A radiation

As a similar idea to the question A compound that absorbs all visible light, I am curious if there is a compound (or compounds) that absorb UV-A radiation (shown below)? However, preferable the ...
user avatar
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
  • 984
6 votes
1 answer
355 views

How do I run MP2 and/or CCSD-level hyperpolarizability calculations with GAMESS?

I have used GAMESS before for TDHF (RPA) / TDDFT level first hyperpolarizability ($\beta$) calculations. However, I cannot figure out how to calculate $\beta$ with MP2 and CCSD for comparative ...
ComputationalNovice's user avatar
6 votes
1 answer
3k views

If I have a chiral substrate, should I always assume that both enantiomers are present?

Considering the Sn1 reaction of (S)-2,3-dimethyl-3-pentanol, knowing that this molecule has a chiral carbon, should I always assume that both enantiomers are present, and therefore the products of a ...
Leonardo's user avatar
  • 2,168
5 votes
3 answers
662 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 ...
Chloritone_360's user avatar
5 votes
2 answers
2k views

Why is FEP transparent and PTFE not?

fluorinated ethylene propylene (FEP) is close relative of poly(tetra-fluoroethylene) (PTFE), both only contain fluorine and carbon atoms,both have very similiar properties yet FEP is relatively ...
wav scientist'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
5 votes
1 answer
194 views

Optical techniques for kinetics studies

What optical methods can be used to measure the concentration of reacting gases in a reactor during an exothermic and fast reaction? I need to monitor and measure the local concentration of my gases (...
SarvF's user avatar
  • 53
5 votes
1 answer
260 views

Behaviour of element 111

Is element 111 considered to act as an eka-aurum? Being under the same column of group 11, which usually provides enough evidence for correlation of properties for an eka-element, would this element ...
čaritisio's user avatar
5 votes
0 answers
46 views

Is there any molecule describable by three-level with mixed parity and transition dipole moments in different directions?

I would like to know if there are molecules described by a three-level system with mixed parity and transition dipole moments in different directions. By mixed parity I mean all three transitions can ...
Pu Zhang's user avatar
  • 155
4 votes
1 answer
5k views

What happens when (+) 2-iodobutane is treated with NaI in acetone?

After treating the compound with NaI, we should follow SN2 mechanism and the product will follow an optical inversion, giving us (-)2-iodobutane, but the answer is (±)2-iodobutane. After going ...
kiv's user avatar
  • 209