New answers tagged

1

According to given data, you may consider expected peak patterns are not complicated such as $\mathrm{ABX}$ or $\mathrm{A_2B}$ patterns (more reading look here. This is simply a $\mathrm{A_2X}$ pattern ($\delta_X = \pu{6 ppm}$ and $\delta_A = \pu{1 ppm}$ without geminal coupling of two $\ce{H_b}$ protons), and hence, peak is a $dt$ for $\ce{H_b}$ as ...


2

Hyperconjugation is indeed very difficult to practically in cases involving bridgehead protons. The underlying reason is essentially the same that also explains why these protons cannot be enolised if there is a carbonyl group adjacent to them. This is best explained by drawing out the compound in a three-dimensional manner, which I have done for you in the ...


3

More resonance structures does not necessarily mean more stabilization. Phenolate has a negative charge at an oxygen atom which cannot be shared without "disturbing" the aromaticity of the ring. This is in part because in the resonance structures drawn, there are negative charged carbons within the aromatic ring, which either implies that: The ring is ...


1

Cross conjugation is a phenomena due to which (in simple words) resonance from two groups in opposite direction cancel out. It is a destabilising effect. It is something like this: These are some examples which will help you understand why this is a destabilising effect: In the above two examples the stability of carbanion decreases drastically as the two ...


2

The thermometer that records the temperature is in the air high above the solution (usually above a Vigreux column). Your distillation was under ambient conditions, so there was air in contact with everything. The thermometer can only records a rising temperature if the temperature around it rises. During the distillation, this is due to methanol vapour (...


4

Vitamin E acetate, or α-tocopheryl acetate, exists in two forms: D-form (solid/highly viscous at 20 °C) and a racemate (viscous liquid at 20 °C). Interestingly enough, the difference in physical properties is well denoted in German Wikipedia article, whereas English Wikipedia omits this. Also, I noticed many authoritative sources arbitrarily listing a ...


0

To my knowledge, comparing the steric hindrance of the carbonyl group is not the path you want to follow to answering this question, because the trigonal planar configuration of the carbonyl carbon provides plenty of room in order for the inductive effect to outweigh the steric hindrance. We have to examine the partial positive charge of the carbonyl carbon ...


0

With the preferred IUPAC name (PIN), there is exactly one way that you expect to find a compound written. Assume you want to buy the compound from the chemical supplier of your choice but don’t have a CAS number at hand. What do you do? You search for the compound in the catalogue. In the old days, these were always paper books that you could use as a ...


3

Essentially, both descriptions are identical. However, they use different phrasings. What Carey and Sundberg mean when they say no allylic stabilisation is essentially that the cation itself is not in an allylic position; that there is no single (non-phenylic) double bond in α-position. To reach the allylic double bond in the β-attack case, you ...


0

A>B>C. In structure A all the carbon atoms as well as nitrogen atom has octet configuration in their valence shell, making it more less energetic and more stable. Whereas B and C have atleast an atom that does not have octet. Further in B the positive charge on the carbon atom is close to lone pair of nitrogen. This results in more attraction than in case of ...


3

cis and trans are perfectly valid descriptors for linear disubstituted alkenes. The (E) and (Z) system is more comprehensive for alkenes, as it also covers trisubstituted and tetrasubstituted alkenes which cis/trans by definition cannot (although some might extend it anyway). In most cases, it would be perfectly reasonable and possible to replace every ...


4

That is because the E/Z-system is an extension of the cis/trans-system. So both systems can be applied to a certain amount of structures and the E/Z-system is then able to treat more advanced systems. From my perception, it seems that Chemistry is a very stubborn … or maybe just very conservative … field where especially new naming conventions get hardly ...


6

Sulphur does not expand its octet. That was a hypothesis proposed long ago and vehemently supported by Linus Pauling. While Linus Pauling had a few very great ideas that moved chemistry forward, he also made some major blunders like the octet expansion hypothesis or seven grams of vitamin C a day. Possibly because of Pauling’s status and Nobel Prize, octet ...


0

This may be the same as other answers, but viewed a different way. Imagine a strong base were to remove the (most acidic) proton attached to nitrogen in pyrrole, giving a structure isoelectronic and isostructural with furan. With the lone pair on the most electronegative atom in both cases we would then expect similar dipole moments (the charge on our ...


-2

http://guweb2.gonzaga.edu/faculty/cronk/CHEM440pub/thioesters.html "thioester cannot make as much of a contribution because the required overlap between carbon's 2p orbital and the sulfur 3p orbital is ineffective. The large difference in energy between these two orbitals means they cannot "mix" as well as the 2p orbitals of oxygen and carbon."


1

The way you put it that everything wants to achieve noble gas configuration is a good rule of thumb for predicting molecules that are stable and long-lived. However, not everything is in equilibrium. A methyl cation certainly exists, and it certainly wants to achieve the noble gas configuration, but it still takes time to do so. So we can conclude that the ...


1

TLDR: Sulfuric acid act as catalyst in the isomerization reaction of parafin hydrocarbons and sometimes it produce undesired sideproducts like sulfonate salts, napthenic acid, bisulfite ions etc. from incomplete oxidation. It follows "hydrogen exchange mechanism. Long answer: @andselisk cited some papers that shows that sulfuric acid can act as a catalyst ...


1

The conjugate base of compound A becomes aromatic post deprotonation: This is essentially a cyclopentadienyl anion derivative, that has 6 $\pi$ electrons that are delocalised over the ring. Thus this compound will be by far the most acidic. As for the other cyclopentadiene derivative, it cannot be deprotonated to make it aromatic: it is localised on an $...


1

Ascorbic acid reacts with bicarbonate: $$\ce{H2Asc + 2 HCO3- -> Asc^2- + 2 H2O + 2 CO2 ^}$$ Ascorbate as a strong reduction agent reacts with oxygen: $$\ce{2 Asc^2- + O2 + 2 H2O -> 2 DHA + 4 OH-}$$ where $\ce{DHA}$ is dehydroascorbic acid. If the ascorbic acid solution is alkalized by sodium hydroxide, the solution slowly turns yellow as the ...


7

You get sulfinic acids $\ce{RSO2H}.$ This paper by Dowson et al. [1] states that Grignard plus $\ce{SO2}$ gives sulfinic acids and as a reference quotes an older article by Allen Jr. et al. [2] which states The reaction between sulfur dioxide and Grignard reagent has been widely used for the preparation of aromatic and aliphatic sulfinic acids. I would ...


4

Nitrosyl cation, $\ce{NO^+}$, is a better electrophile than molecular $\ce{HNO3}$ (you don't get $\ce{NO_2^+}$ in this system without sulfuric acid or other strong auxiliary acid) and so you get nitrosobenzene in the substitution reaction. But then the nitrosyl group with its nonbonding electron pair is an attractive target for oxidation by the nitric acid ...


1

At $\mathrm{pH}=\mathrm{p}K_\mathrm{a}=3.75$ , there will be 50% of non-dissociated formic acid and 50% of formiate. You need 50 % of stoichiometric amount of hydrochloric acid to convert 50% of the formiate to the acid. If we consider the percentage as (w/w) %, then $\pu{1 kg}$ of 75% formic acid ($M=\pu{46 g/mol}$) contains $\pu{16.3 mol}$ of formic ...


-3

In my experience with acylations and esterificatio, (both O-acyl and O-propionylations) , a very small catalytic amnt of DMAP (100 mg per mole of product) along with reduced qty of pyridine has allowed the room temp acylation of some normally sterically hindered organics in less than 30 mins. In fact, while working with temp sensitive piperidine based ...


1

All the special rules you need for naming of such dispiro cycloalkane systems can be found in one chapter of Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book): P-24.2.2 Linear polyspiro alicyclic ring systems Polyspiro parent hydrides consisting of unbranched assemblies of three or more saturated ...


4

Molybdenum(VI) fluoride can be used as a fluorinating agent though not as popular as the selective DAST and Deoxyfluor as @Waylander noted. Molybdenum(VI) fluoride fall under the category of electrophilic fluorinating agent where it acts as a Lewis acid. The reaction is run in an inert solvent like $\ce{CH2Cl2}$ and a catalyst like boron trifluoride is used. ...


0

Partial answer You can find the reference here: Leopold, K. R., & Haim, A. (1977). Equilibrium, kinetics, and mechanism of the malonic acid-iodine reaction. International Journal of Chemical Kinetics, 9(1), 83–95. doi:10.1002/kin.550090108 It's mechanism is , which is not quite exactly same as yours. It involves $\ce{I_3^-}$ ions. The widely ...


1

I'd expect $\ce{H2O, CO, CO2}$, and $\ce{SO2}$ to be created during the combustion of these compounds. I'd wager a decent amount of $\ce{SO2}$ was created, but was diluted in the atmosphere. Regarding $\ce{H2S}$, maybe it was produced, but then reacted according to the following: $$\ce{H2S + O2 -> SO2 + H2O}$$ Additionally, there were probably a wide ...


5

As the significance of the two contrasting factors cannot be easily evaluated, let us first look at some evidence. Wan, Modro & Yates (1980) reported the $\ce {pK_a}$ values of the conjugate acids of the various lactams, as shown in the table below: \begin{array}{|c|c|c|c|} \hline \text{Lactam} & pK_a\\ \hline \ce{$\beta$, 4} & -0.96\\ \hline \...


5

The most important simplified criteria for the choice of a principal chain are: greater number of substituents corresponding to the suffix (principal characteristic group) longest chain greater number of multiple bonds lower locants for suffixes lower locants for multiple bonds greater number of prefixes lower locants for prefixes lower locants for ...


8

According to the current version of Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book), as already mentioned in the question, the first relevant criterion to be considered in choosing a principal chain is the length of the chain. When there is a choice for the principal chain, the following criteria are applied, ...


0

“unless I am allowed to substitute the additional H on the 2-methylpropane with a Cl” I assume your confusion lies on the fact that Cl substitutes preferably the H that bonds with a primary carbon, whereas Br would substitute preferably the H that bonds with a tertiary carbon. This is of course correct and this would be the main product. However, a small ...


3

In the paper "(Cyclobutadiene)iron Tricarbonyls - A Case of Theory before Experiment", Organometallics 2003, 22, 2-20 https://pubs.acs.org/doi/pdf/10.1021/om020946c, at the page 12 nice explanation of bonding in this compound is provided: The electronic structure of (cyclobutadiene)iron tricarbonyl has been the subject of many papers. He I and He II low-...


9

Carbamates are usually reduced to N-methyl groups. There are numerous examples: J. Am. Chem. Soc. 2012, 134 (16), 6936–6939 Org. Lett. 2012, 14 (18), 4834–4837 But it is not always a given. In this next example, the nitrogen is part of a three-membered ring (aziridine). These nitrogens are better leaving groups than usual, cf. Ketone/aldehyde synthesis ...


1

The following is the abstract of K.M. Zhang "Selective Nitration Of Benzyl Chloride And Its Application In The Synthesis Of Nitrobenzaldehyde"(link). The full pdf is behind paywall. The selective nitration of benzyl chloride and its application in the synthesis of 4-nitrobenzaldehyde were studied. Nitration of benzyl chloride with $\ce{HNO3}$ in the ...


18

It is the temperature of the pan that matters not the flame The flame temperature is irrelevant if you are cooking in a vessel. the only temperature you need to worry about is the temperature of the surface of the pan (or–even more importantly–the temperature of the meat). The surface of the pan will rarely get above around 220 °C if you are monitoring it. ...


10

Nothing with more thermal mass than a needle will reach the temperature of the flame. Note that if the stove or utensils would be this hot they would be glowing blinding white, while IRL they won't even glow a dim red. Granted if you dripped fat on a hot stove it would turn into a black tar containing PAH's, and a microscropic fraction of this could end up ...


2

I just looked in the literature, and it has been done even without catalyst in a "reactive distillation column" at high temperatures (patent US201113194873). If you can remove the water formed, you can technically drive the reaction forward, even if it is slow. A catalyst will just make that process easier, requiring less heat and time. Phosphoric acid is a ...


2

The answer given by @M. Farooq may be interpreted as «the optimization of TLC depends on the choice of the eluents used, which till now (by broader advent of machine learning) was empirical». In my opinion, this should not the impression to retain. Of course the optimization of TLC depends 1) on the eluent / eluent mixture, but should be seen in context of ...


5

The Suzuki coupling reaction (also called Suzuki-Miyaura coupling reactions; Ref.1) is the coupling of an aryl or vinyl boronic acid with an aryl or vinyl halide or triflate using a palladium(0) catalyst similar to Heck reaction and Negishi reactions in mechanistic aspects. In particular, Negishi reaction uses organozinc reagents instead of organoboronic ...


2

I can give a very pictorial answer that doesn't require the use of actual pictures nor typesetting and might useful for beginners. It is all about the misconception, encountered even in chemists with a relative experience in successful experiments, that solubility of the compounds in a mixture is a key factor for their effective chromatographic separation ...


5

Chromatography is really an empirical science. The fluid mechanical side and the adsorption phenomenon is somewhat well understood but choosing mobile phases is essentially based on trials, sadly to date. If someone has given you a ratio, say 8:2, it means someone must have tried it and they found that this mobile phase works the best. The main criterion for ...


2

The reaction of the ketal 1 with aqueous H2SO4 is more likely to follow the pathway 1 --> 2 --> 3 to form α,β-unsaturated ketone 3. This is a typical ketal hydrolysis in acid medium. For the proposed reaction pathway 1 --> 4 --> 5 --> 6, species 6 is unstable. Indeed, if it were formed as an intermediate, it would afford ester 7a and ultimately ...


2

Many organic reactions' steps may be described by equilibria. In other words, at least on microscopic scale, both «forward» and «backward reaction» is possible. So a homework for you is to become fluent in this reversibility. As an example relevant here: I'm not aware about an better approach than to learn a handfull of rearrangement reactions till you ...


1

In electrospray ionization, a molecule can end up with an extra proton or an extra cation. Either one of these +1 charged species is accelerated and detected in the mass spectrometer (negative charged particles or neutral species are not; if there are multiple cations, they would supposedly repel each other once the solvent is gone, and not fly together). ...


-1

In3,5 dimethyl 4 nitro phenol , the nitro group is between two ortho methyl groups . Therefore due to this steric inhibition of resonance occurs and this nitro group is pushed out of plane by two methyl groups. Such that nitro group does not take part in the resonance. And there have no extra stable structure. That is why it is less acidic than2,6 dimethyl 4 ...


2

I think OP is confused with the colorimetric method of detection of piperine, which uses the concentrated sulfuric acid as one of reactant with chromotropic acid, 1,8-dihydroxynaphthalene-3,6-disulfonic acid (Chromotropic Acid Test; Ref.1 & 2). Accordingly, this colorimetric method, developed in 1965, relied on hydrolyzing the methylenedioxy group of ...


3

I think all modern teaching labs use attenuated total reflectance (ATR)-FTIR systems... you place some crystals and then collect the spectrum right away. ATR is least sensitive technique because the IR penetrates only only a few nanometers of the sample. In good old school times, one would dry the sample-literally bone dry, then oven-dried KBr was ground ...


2

The alleged original RSC source for this reaction was not accessible online.1. However, Olah et al. have reported2 that α-naphthol 1 in superacid medium forms a dication species 4. The use of excess AlCl3 provides a mechanism for the formation of superacid 3. Benzylic dication 4 undergoes substitution of o-dichlorobenzene 5 which ultimately forms the ...


3

I believe the concept assessed here is the idea of aromaticity. You must first be able to recognise that the lone pair held by each carbon atom with the negative formal charge is in a different type of orbital. In the carbon atom of the 6-membered ring, it is in an $\ce {sp^2}$ hybrid orbital that is in a plane perpendicular to the $\pi$ electron cloud of ...


0

Axial methylcyclohexane has two gauche interactions. One is between the CH3-C1 bond and the C2-C3 bond shown in red. The dihedral (torsional) angle is ~60o. Given the plane of symmetry passing through CH3-C1-C4, the second gauche interaction is on the opposite side of the plane (CH3-C1 bond and the C6-C5 bond). Each of these interactions is worth ~0.9 kcal/...


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