Spectroscopy is the study of the interactions between matter and radiated energy. Experimentally, the results are returned as a function of wavelength versus amplitude (intensity), where the spectral lines represent the resonance frequency of the sample.

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Assigning IR of [Cu3(btc)2]

I am trying to identify the peaks due to the carboxylate groups in the IR of $\ce{[Cu3(btc)2]}$. I think that the large peaks at $1643.76~\mathrm{cm^{-1}}$ and $1369.19~\mathrm{cm^{-1}}$ are both ...
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69 views

How to explain the discrepancy between the calculated absorption wavelength within the particle in the box theory and the observed wavelength?

The experimental observed wavelength for this molecule is 425 nm. We are supposed to estimate this wavelength theoretically using this equation (energy change in a 1D box), where $N$ is the number of ...
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65 views

How to identify the number of pi electrons in a conjugated system to calculate the HOMO-LUMO gap with the particle in the box approach?

It's my understanding that for a particle in a 1-D box, the change in energy from the HOMO to LUMO can be approximated with the following equation: $$\Delta E=\frac{h^2 ( N + 1 )}{8 m_\mathrm{e} ...
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20 views

Proportionality between number of absorbed photons and optical density

I am to show that the number of absorbed photons only is proportional to the optical density at low optical densities. I do not know how to do this, but this reminds me of the linear range of ...
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13 views

Effects on Stretching Frequencies in Organometallic Complexes

If you added a negative charge to $\ce{Mo(CO)_6}$ how would this effect the $\ce{CO}$ stretching frequency in an IR spectrum? My thoughts are that it would lower the $\ce{CO}$ stretching frequency ...
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19 views

Calculating Raman Intensities from Static Raman Activities

Whenever I want to calculate a Raman spectrum, my quantum chemical programs give me Raman scattering activities. As the common Raman spectrum is dependent on the incident wavelength of the used laser ...
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38 views

Proton NMR of ($\eta^6$-mesitylene) tricarbonyl-molybdenum $(1,3,5-C_6H_3Me_3)Mo(CO)_3$ [closed]

I'm trying to assign the Proton NMR of ($\eta^6$-mesitylene) tricarbonyl-molybdenum $(1,3,5-C_6H_3Me_3)Mo(CO)_3$ Apologies for the poor quality of the spectrum but there are two peaks one at ...
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34 views

How calculate spectral overlap integral using spreadsheets?

I need to calculate the spectral overlap integral for the emission spectrum of coumarin 334 and the absorption spectrum for rhodamine, using spreadsheets (MS Excel). Following the theory of ...
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32 views

Comparing IR stretching bands in molybdenum complexes

Why would the infrared stretching frequency of $\ce{CO}$ (which is about $2140~\mathrm{cm^{-1}}$ in gaseous form) be $1982~\mathrm{cm^{-1}}$ in $\ce{[Mo(CO)_6]}$ and even lower in ...
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32 views

Propose a structure base on the molecular formula and 1H NMR spectrum [closed]

The molecular formula is C9H8O4. I came up with the structure known as caffeic acid but it does not match the some of the peaks. I know that there has to be a benzene ring along with two double ...
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36 views

Assigning Mass Spectrum of $\ce{(NPCl2)3}$

I'm trying to assign the mass spectrum of the heterocyclic compound $\ce{(NPCl2)3}$ The mass spectrum is as follows: My annotations show that I think the molecular ion is the peak at 346.9 m/z and ...
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17 views

Infrared Spectroscopy of Hexachlorocyclotriphosphazene

When assigning the IR spectrum of hexachlorocyclotriphosphazene there are two prominent peaks (one due to the nitrogen-phosphorus bond and the other due to the phosphorus-chlorine bond). There is ...
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15 views

Could IR and Raman be measured simultaneously?

IR and Raman are measured using two different machines. Looking at the nature of excitation and at the way data is collected, it seems that these two measurements could be done simultaneously (or with ...
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1answer
75 views

Peak Wavelength of Emission Spectrum of a Flame vs. Actual Flame Temperature

I am looking at a lab test of two variants of mixed hydrocarbon gas (57.8% $H_2$, 16.9% $N_2$, 12.4% $CH_4$, 1.11% water vapor, and 11.8% "unknown" gases) burning in oxygen which shows a discontinous ...
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43 views

What would you recommend to isolate these compounds from cooking oil?

Recycled cooking oil, aka "gutter oil", is a major problem in countries such as China. I am doing some research to see if there's a reliable and quick way to determine if something is gutter oil. I ...
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1answer
97 views

Interchange of axial and equatorial groups in Me2NPF4

The $\ce{^{31}P}$ NMR spectrum of $\ce{Me2NPF4}$ when recorded at room temperature consists of a quintet with intensities $1:4:6:4:1$. However, at $-100~\mathrm{^\circ C}$, the spectrum is as shown ...
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21 views

What is the typical range for the molar absorptivity of paint?

For example, $\ce{TiO2}$ is used a lot as pigments in paint, what is the range of molar absorptivity for that? Would I be able to determine this from this graph: Ideally I could estimate a range ...
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1answer
60 views

Why is the carbonyl IR frequency for a carboxylic acid lower than that of a ketone whilst an ester is higher than a ketone

The approximate stretching frequencies are as follows: Acid: $1710$, Ketone: $1715$, Ester: $1730$ (all $\mathrm{cm^{-1}}$) This would seem to suggest that the acid decreases the carbonyl bond ...
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210 views

Why does an acid anhydride have two infra-red stretching frequencies

The carbonyl stretching frequencies for an acid anhydride are approximately $1820\rm~cm^{-1}$ and $1760\rm~cm^{-1}$. These are both higher frequencies than a simple ketone owing to the electron ...
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31 views

spectroscopy as a pharmaceutical career [closed]

Is studying spectroscopy form it's fundamental perspective regarding "group theory" , "molecular schrodinger equation" and theoretical basis for IR & Raman analysis important for pharmacists ...
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1answer
59 views

Interpretation of 1H-NMR spectra for Z-ochtodenol

I'm struggling to understand the 1H-NMR data for this compound. I managed to find the compound using the data I had, but at the end I can't assign the peaks properly. My confusions are: ...
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1answer
26 views

Why absorption/transmission spectroscopic data is normalized?

A typical data processing step for acquired absorption/transmission data is normalizing, i.e. stretching the curve such that it is bounded between 0 and 100%. However, the absorption/transmission ...
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1answer
59 views

Why can't carbon and nitrogen be detected in ICP-MS and ICP-OES techniques?

Why can't carbon and nitrogen be detected in ICP-MS and ICP-OES techniques? My book says this technique is efficient for detecting multiple elements, with exception of halogens and carbon. I found ...
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72 views

Hydrogen's confusing purple glow

While reading about hydrogen on Wikipedia, I read that hydrogen has a purple glow in its plasma state. This confused me because although hydrogen is present in its plasma state on the sun, the sun ...
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58 views

Tables/database/literature of specific or optical rotation

I'm looking for a comprehensive reference of experimental specific rotation or optical rotation data. It can be a published literature review, a free web database with API access or one that permits ...
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22 views

Observe from IR/Raman spectra whether molecule is in a local minimum on PES

I have done a geometry optimization of cis and trans-difluoroethene using RHF/STO-3G in Gaussian03. Although this is a simple method and a small basis set, this should ideally put place the molecule ...
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1answer
105 views

How much worse is methane than CO2 as greenhouse gas? [duplicate]

I can't find a coherent answer to this question. The numbers are all over the place. 25 times greater 84 times more potent The reason I'm looking is because I can't find a reason in physics why ...
3
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28 views

FT-IR background lines

I started doing IR spectroscopy a few months ago and have run into the following problem: Here's the IR background that everyone knows and loves: CO2 peaks in the middle, water lines on either side. ...
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1answer
185 views

Conflict Between Organic and Physical Chemists--explaining the intensities of IR absorptions

I am currently a Chemistry undergrad and I love to fact check everything my O Chem professor says against my research advisor, a physical/computational chemist. Well, my O Chem professor, when ...
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2answers
91 views

Shifting of axial and equatorial protons

I know this NMR represents cyclohexanol and I have figured out what each peak represents. If the 3 peaks at 1.9, 1.7,1.5 all represent equatorial protons as they are shifted downfield compared to the ...
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1answer
82 views

NMR analysis problem

I've been given this NMR along with the IR and Mass Spec and assigned the task of figuring out the unknown compound. I know that it is cyclohexanol and by analysing the NMR I know that the peak at ...
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45 views

Calculating binding energies for excitated levels in potassium?

Suppose a laser is used to excite electronic transitions in potassium from the $3p$ orbitals to ones higher than $4s$. When I attempt to use the Bohr model to calculate binding energies, what I obtain ...
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33 views

Mass Spec - What could a loss of 28amu as the first fragmentation be?

I guess 28 could be CO, C2H4 or N2. However I can't work out a mechanism by which CO could be the first fragmentation of any common organic compound. It seems like a diazonium salt could lose N2 as ...
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66 views

Calculate radius of gyration (Rg) and molar mass from light scattering data (Rθ and θ/degree)

I have a homework problem that I don’t have a solution for, so I would like understand how to solve it and to know if my suggested way of solving it is on the right track. The problem is as following: ...
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1answer
45 views

Radiationless energy transfer: how to arrive at the equation that give R0 between two chromophores?

I have a homework question where I should calculate $R_0$ of an energy transfer between two chromophores. However, I don't understand how my professor arrived at the equation that we should apply ...
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2answers
86 views

H NMR of 4-chloroacetophenone

For the H NMR of the compound I am wondering why peak (A) is the farthest out of all of them? I think that it is due to the electro negativity of oxygen. Am I correct? If so, why would the presence of ...
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1answer
257 views

Why is it possible to image LUMO if these orbitals are, by definition, unoccupied?

LUMO stands for lowest unoccupied molecular orbital. If it's unoccupied, how is it possible to image it? See for example in this paper ("Pentacene imaged with STM and NC-AFM").
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108 views

How does absorption spectroscopy work?

So a beam of white-light photons passes through a gas and various photons, having exactly the same energy as the gas's molecular energy transition state deltas, get absorbed. We then get a ...
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19 views

How to assign various UV peaks for Methotrexate for the individual moities present in the molecule

Major peaks are obtained at 260 nm, 310 nm and 370 nm. 370 nm could be due to 2,4-pteridinediamine moiety. How to account for the other two values
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49 views

What is the role of a monochromator in AAS?

What would happen if we didn't use a monochromator; i.e. what is its role in Atomic Absorption Spectroscopy?
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46 views

Can you read the concentration of X on an UV standard curve?

I was in lab some days ago and got my lab report back. My professor said something I didn't understood. It was something about my standard absorption curve (UV) for caffeine. I made a curve, where ...
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89 views

Have Mossbauer spectroscopy on 67Zn ever been used to study Zinc containing enzymes?

Have Mossbauer spectroscopy with 67Zn as absorber and 67Ga as emitter ever been used to study zinc containing enzymes? The perfect answer will contain link to article/book where example of 67Zn usage ...
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1answer
32 views

Why highly unstable cyclic boron compounds should be stabilised by two electron reduction?

I am trying to figure out why highly unstable cyclic boron compounds (such as the one below) could be stabilised by two electron reduction... My thoughts are because each Boron has an empty ...
6
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2answers
270 views

Atomic emission spectra: classical vs. quantum mechanics

In class, we were first introduced to classical mechanics, and how Bohr used the hydrogen electron to explain the atomic emission spectrum of that element. And it made sense. But then classical ...
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142 views

How to find the final and initial n values from an emission spectrum line?

A line is observed at 102.6 nm. Determine the values of n for the initial and final energy levels of the electron during the emission of energy that leads to this spectral line. I have been ...
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1answer
43 views

Why does Stokes raman not relax to the ground state while anti-Stokes does?

I'm just wondering why stoke-Raman doesn't go to the ground state. Where does the rest of energy from exciting laser leave? On the other hand, why does anti-stoke go back to ground state? I know that ...
6
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2answers
301 views

1H (proton) NMR spectra for alkanes

I do not fully understand the idea of coupling and why chemically equivalent hydrogens do not couple. I wanted to work with the alkanes, so let's take propane first: There would be a triplet ...
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1answer
64 views

Determination of brominated aromatics by 13C and 1H NMR spectroscopy

How can I identify 4-bromoazobenzene, 4-bromoazoxybenzene, and 4,4’-dibromo-$\ce{N,N}$’-diphenylhydrazine products using $^1\ce{H}$ and $^{13}\ce{C}$ NMR? I’m really confused by the general shape of ...
3
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1answer
166 views

Deducing compounds from spectroscopic data for isomers of formula C4H8O

Here's the problem: I've already know the 3600 cm$^{-1}$ line indicates the $\ce{-OH}$ group and the 1640 cm$^{-1}$ line indicates the C double-bond C alkene. From the $^{13}$C NMR data: the two ...
7
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1answer
117 views

What is the difference between infrared action spectroscopy and conventional IR spectroscopy?

I'm familiar with infrared spectroscopy generally, which probes mainly the vibrational behavior of molecules under study. However, I'm seeing references in various literature to 'infrared action ...