Questions tagged [physical-organic-chemistry]

For questions about how organic molecules and reactions are investigated using physical experiments.

22 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
7
votes
0answers
288 views

What can we say about the dipole moment of terephthalic acid?

The dipole moment of quinol is not zero because it can exist in two different energetically favourable conformations. The weighted average is calculated to arrive a dipole moment of 1.6 D. According ...
5
votes
0answers
31 views

Does π values vary in Hansch-Fujita equations for a given substituent?

I was reading about Hansch-Fujita equations from Hansch-Fujita paramaters and observed that the $π$ values of substituents (analogous to Hammet $σ$ values) change according to the specific environment ...
5
votes
0answers
88 views

How do bonds rotate in pericyclic reactions?

In Pericyclic reactions, it is shown that the terminal bonds rotate (conrotation or disrotation) to allow for allignment of the FMO's, thereby forming the sigma bond However, a detail that most of my ...
4
votes
0answers
23 views

Normalising Kinetic Isotope Effect Per Deuterium Atom

I've synthesised a protic and deuterated version of a specific molecule where there are two deuterium atoms in the latter. I then go about and measure the kinetic isotope effect (KIE) for a reaction ...
4
votes
0answers
112 views

Number of configurations/states for electrons in orbitals

I'm performing complete active space calculations for the prediction of X-ray absorption L edge spectra. This involves an excitation from 2p orbitals to the 3d orbitals of the metal. For the ...
3
votes
1answer
53 views

Comparing rates of substitution reactions

The following question was asked in an exam I gave recently Compare the overall rates of the following substitution reactions $$\ce{CH3Cl ->[OH-][Weak P.A.S] CH3OH}$$ $$\ce{CH3CH2Cl ->[OH-][ ...
3
votes
0answers
52 views

Can cycloaddition reactions be antarafacial?

Cycloaddition reactions of the form [4+2] and [2+2] are always suprafacial, as the geometry is too constrained to allow for antarafacial interaction between the FMO's. However, for cycloaddition of ...
3
votes
0answers
137 views

Why does Larmor precession occur in NMR?

Larmor precession is the phenomenon that in NMR the spin (and by default also the magnetic dipole moment) of protons does not line up with the applied magnetic field but rather precesses around this ...
2
votes
0answers
55 views

Why is the enthalpy of formation of 2,2-dimethylpentane larger than that of 2,2,3-trimethylbutane?

Firstly, it is commonly known and taught that branched alkanes are more stable than linear ones, and so have larger enthalpies of formation. But why is that the case? Are there some steric ...
2
votes
0answers
25 views

What kinetic model does the hydrogenation reaction of dibenzyltoluene follow?

So during the course of my research, I've read countless papers related to the hydrogenation of dibenzyltoluenen and the dehydrogenation of perhydro-dibenzyltoluene. Now what I've noticed, is the fact ...
2
votes
0answers
81 views

pKa of acetic acid in pure NH3?

Acetic acid completely dissociates in liquid ammonia and I would like to know the $\mathrm{p}K_\mathrm{a}$ value for the acid in that solvent. Can anybody point me to a reference?
2
votes
0answers
36 views

Origin of the NMR shielding

In a paramgnetic material the induced dipole moment of atoms or (molecules) of the material aligns with the external field. I can understand this by Zeeman splitting. A term symbol splits into states ...
1
vote
0answers
22 views

How do electrostatic effects effect facial selectivity in addition to cyclic oxo-carbeniums?

I was reviewing Dave Evans' notes for stereochemistry of C=X electrophile additions, and found this slide detailing differences in additions to cyclic oxo-carbenium electrophiles, but I don't ...
1
vote
0answers
50 views

Comparison of boiling points of para-derivatives of phenol

The boiling points of four para-derivatives of phenol are: How can we compare the boiling points of p-nitrophenol and p-aminophenol? Apart from the hydroxyl group, p-nitrophenol has two oxygen atoms ...
1
vote
0answers
29 views

Would the initial step of this mechanism be exothermic or endothermic? (Protonation)

My understanding is that since an O-H bond is being formed, the protonation step must be exothermic because energy is released upon bond formation. However, if I were to draw an energy/reaction ...
1
vote
0answers
16 views

What is the influence of citrate on PEG-modified polyacrylamide hydrogels?

I've been having a puzzle explaining the experimental results with the citrate anions and PEG modified polyacrylamide: According to the experimental data there is a hydrogel swelling whenever citrate ...
1
vote
0answers
43 views

Primary kinetic isotope effect

Why does the transition state in both protonated and deuterated molecules have the same energy? My textbook assumes that during transitional state the isotopic bond is half-broken or on its way to ...
1
vote
0answers
49 views

Volatility comparison for isomers of phthalic acid

All the atoms of these compounds are in a plane. o-phthalic acid can show extensive intra-molecular hydrogen bonding as well as inter-molecular hydrogen bonding. m-phthalic acid can show intra-...
1
vote
0answers
29 views

Enantiomeric excess catalysed

Enantiomeric excess is defined as $$ee = \frac{[R]-[S]}{[R]+[S]}$$ I found this problem in an IChO paper: "When using the enantiomerically pure (BINOL)Al(OiPr) as a catalyst for reduction of ...
0
votes
0answers
28 views

Why does Red Phosphorus react so violently with an oxidizer like Potassium Chlorate?

In Armstrong's Mixture, mixing those two chemicals results in a friction sensitive explosive which produces a loud bang. According to wikipedia, it is made by adding a strong oxidizer to red ...
0
votes
0answers
29 views

A question about potential difference across a membrane

Membrane potential of living cells arising from the difference of concentration of ions on both sides of the membrane, but why didn't someone use selective polymers as AEM (Anion Exchange Membrane) ...
0
votes
0answers
34 views

What is the justification for using the Marcus rate equation to model charge transport in organic semiconductors?

I am trying to understand the history of how Marcus theory moved from describing electron exchange reactions in aqueous ionic solutions to also being applied to describe transport in organic ...