Libermann's nitroso reaction

 nitroso reaction

While phenol is reacted with NaNO2 and concentrated H2SO4, it provides a deep green or blue colour which changes to red on dilution with water. while generated alkaline along with NaOH original green or blue colour is restored. This reaction is termed as Liebermann's nitroso reaction and is employed as a test of phenol.

COMPOUND K22 KILLER OF SARS AND MERS

Scientists find killer chemical for virus behind SARS and MERS

 RCharles Watson, Curtin University

A team of European researchers has identified a novel compound that stops coronaviruses from replicating. The study, published in PLOS Pathogens today, also pinpoints the juncture in the virus’ life cycle when the compound works, suggesting vulnerable stages in virus replication that might be attacked by different antiviral compounds.

Coronavirus infections are primarily found in animals, but have recently spread to humans, causing serious respiratory illness.

The coronavirus was behind the 2003 SARS (severe acute respiratory syndrome) epidemic, which killed 775 of the 8,283 people infected. It’s also the cause of the MERS (Middle East respiratory syndrome) outbreak in Saudi Arabia over the past two years. MERS has killed almost 200 people and infected 600. The MERS coronavirus seems to come from human contact with camels.

Currently, there’s no specific antiviral treatment that’s effective against coronaviruses.

A promising compound

Coronaviruses replicate themselves by taking control of normal cellular machinery to manufacture new virus particles. An early step in this process is “stealing” membranes made by normal cells in order to make the viral capsule.

This viral capsule then forms a coat to protect its RNA, which is the heart of the virus. The infected cell becomes packed with newly manufactured viral particles and they burst out to infect other cells.

The authors of the paper published today found a compound called K22 stops the formation of the viral capsule, and so stops the replication of the virus. The discovery was based on a shotgun approach to finding potential antiviral drugs; the researchers tested over 16,000 chemical compounds to determine which, if any, killed coronaviruses.

The compound K22 worked well against a relatively harmless coronavirus in the initial tests, and was then found to be equally effective against other coronaviruses. Those tested included the coronaviruses that cause SARS and MERS.

This finding led the researchers to examine in detail what actually happened to the virus cultures when treated with K22.

They found K22 stopped an early stage of virus formation – the construction of a viral coat or capsule using material normally produced by the cells they infected.

The long road ahead

While this is an important discovery, it doesn’t mean we’ll soon be able to use this antiviral compound in humans.

Once a promising compound like this is identified, there’s a rigorous process of carrying out animal trials, development of variations (analogues) that might work even better, and finally, human trials. All these steps determine whether the compound is both safe and efficient for dispatching its intended target.

One promising feature of the K22 compound is that its ability to act early in the viral replication process means it (or its derivatives) could be effective against a wide range of coronaviruses.

While the discovery of a compound with promising antiviral activity is certainly important, the transition from lab to treatment of human illness is a long and uncertain one.

The authors of the article emphasise their discovery:

is only the very first step towards an approved drug for therapeutic use in animals or humans.

Coronavirus: a short history

Before the SARS epidemic in 2003, it was known that coronavirus infections were common in a wide variety of domestic and wild mammals and birds. These viruses can cause significant illness in farm cows and pigs. And one type of coronavirus is a well-known cause of the common cold in humans.

The identification of the SARS virus changed all this, because it was rapidly transmitted from human to human – with a death rate of almost one in ten. The virus seems to have originated in bat populations in China and other parts of southeast Asia. It was transmitted to wild civet cats, which are sold in markets in Asia, and onto humans.

SARS affects not only the upper respiratory system but also the lungs, as well as causing gastroenteritis. The lung infection causes pneumonia, and the bowel infection ensures the virus is transmitted by faecal contamination of fingers and hands.

The MERS coronavirus is related to a strain common among bats living in caves on the Arabian peninsula. Camels go to the caves to drink water, and may have became infected in this way.

Humans in close contact with camels were then infected. But there’s some good news – MERS is not transmitted as easily as SARS. Still, it has a death rate of around 40%, so there’s cause of concern. 

Reference by :Charles Watson

Chirata (swertia)

Swertia is a genus in the gentian family containing plants sometimes referred to as the felworts. Some species bear very showy purple and blue flowers.

What other names is Chirata known by?

Bitter Stick, Bitterstick, Chirayta, Chiretta, Chirette, Chirette des Indes, East Indian Balmony, Genciana de la India, Gentiana chirata, Gentiana chirayita, Indian Bolonong, Indian Gentian, Kairata, Kirata, Swertia chirata, Swertia chirayita, Yin Du Zhang Ya Cai.

What is Chirata?

Chirata is an herb. People use the parts that grow above the ground to make medicine.

Chirata is used for fever, consiption upset stomach , loss of appetite, intestinal worms, skin diseases, and cancer. Some people use it as “a bitter tonic.”

In India, it has been used for malaria, when combined with the seeds of divi-divi (Guilandina bonducella).

In manufacturing, chirata is used in alcoholic and non-alcoholic beverages.

Insufficient Evidence to Rate Effectiveness for.

• Fever.
• Malaria.
• Constipation.
• Worm infestations.
• Upset stomach.
• Loss of appetite.
• Skin diseases.
• Cancer.
• Other conditions.

More evidence is needed to rate the effectiveness of chirata for these uses.

Are there safety concerns?

Chirata is LIKELY SAFE when taken by mouth in the amounts found in beverages. However, there isn't enough information available to know if chirata is safe in larger medicinal amounts.

Special Precautions & Warnings:

Pregnancy and breast-feeding: There is not enough reliable information about the safety of taking chirata if you are pregnant or brestfeeding. Stay on the safe side and avoid use.

Diabetes ;  Chirata might lower  blood sugar  levels in some people. Watch for signs of low blood sugar (hypoglycemia) and monitor your  blood sugar carefully if you have diabetes and use chirata as a medicine.

Intestinal (duodenal) ulcers: Chirata can make ulcers in the intestine worse.

Surgery. Chirata might lower blood sugar. In theory, chirata might interfere with blood sugar control during and after surgical procedures. Stop using chirata as a medicine at least two weeks before a scheduled surgery. 

Corona viruses

Whta is corona viruses ?
Coronaviruses are transmitted through the air and primarily infect the upper respiratory and gastrointestinal tract of mammals and birds. 

 Symptoms of corona viruses

For confirmed 2019-nCoV infections, reported illnesses have ranged from people with little to no symptoms to people being severely ill and dying. Symptoms can include:

• Fever
• Cough
• Shortness of breath 
• Runny nose
• Headache 
• Sore throat  
• Not feeling well overall

Transmission 

    

 Much is unknown about how 2019-nCoV, a new coronavirus, spreads. Current knowledge is largely based on what is known about similar coronaviruses. Coronaviruses are a large family of viruses that are common in many different species of animals, including camels, cattle, cats, and bats. Rarely, animal coronaviruses can infect people and then spread between people.

Most often, spread from person-to-person happens among close contacts (about 6 feet). Person-to-person spread is thought to occur mainly via respiratory droplets produced when an infected person coughs or sneezes, similar to how influenza and other respiratory pathogens spread. These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled into the lungs. It’s currently unclear if a person can get 2019-nCoV by touching a surface or object that has the virus on it and then touching their own mouth, nose, or possibly their eyes.

Typically, with most respiratory viruses, people are thought to be most contagious when they are most symptomatic (the sickest). external icon of spread from an infected patient with no symptoms to a close contact.

It’s important to note that how easily a virus spreads person-to-person can vary. Some viruses are highly contagious (like measles), while other viruses are less so. There is much more to learn about the transmissibility, severity, and other features associated with 2019-nCoV and investigations are ongoing.

Causes of corona viruses 

 In cows and pigs coronaviruses cause diarrhea. In chickens they cause an upper respiratory disease. There are no vaccines or antiviral drugs that are approved for prevention or treatment.

Prevention 

There is currently no vaccine to prevent 2019-nCoV infection. The best way to prevent infection is to avoid being exposed to this virus. However, as a reminder, CDC always recommends everyday preventive actions to help prevent the spread of respiratory viruses, including:

• Wash your hands often with soap and water for at least 20 seconds, especially after going to the bathroom; before eating; and after blowing your nose, coughing, or sneezing.
• If soap and water are not readily available, use an alcohol-based hand sanitizer with at least 60% alcohol. Always wash hands with soap and water if hands are visibly dirty.
• Avoid touching your eyes, nose, and mouth with unwashed hands.
• Avoid close contact with people who are sick.
• Stay home when you are sick.
• Cover your cough or sneeze with a tissue, then throw the tissue in the trash.
• Clean and disinfect frequently touched objects and surfaces using a regular household cleaning spray or wipe.

Spectral properties of Aromatic ring

                       Infrared Spectra

The presence of a phenyl group in a compound can be ascertained with a fair degree of certainty from its infrared spectrum. For example, in Figure 22-1 we see the infrared spectra of methylbenzene, and of 1,2-, 1,3-, and 1,4-dimethylbenzene. That each spectrum is of a benzene derivative is apparent from certain common features. The two bands near 1600cm−1$1600{\text{cm}}^{-1}$ and 1500cm−1$1500{\text{cm}}^{-1}$, although of variable intensity, have been correlated with the stretching vibrations of the carbon-carbon bonds of the aromatic ring; also, the sharp bands near 3030cm−1$3030{\text{cm}}^{-1}$ are characteristic of aromatic C−H$\text{C}-\text{H}$ bonds. Other bands in the spectra, especially those between 1650cm−1$1650{\text{cm}}^{-1}$ and 2000cm−1$2000{\text{cm}}^{-1}$, between 1225cm−1$1225{\text{cm}}^{-1}$ and 950cm−1$950{\text{cm}}^{-1}$, and below 900cm−1$900{\text{cm}}^{-1}$, have been correlated with the number and position of ring substituents. Although we shall not document all these various bands in detail, each of the spectra in Figure 22-1 is marked to show some of the correlations that have been made.

Figure 22-1: Infrared spectra of methylbenzene and the 1,2-, 1,3-, and 1,4-dimethylbenzenes. The number and positions of ring substituents determine the pattern of the low-intensity bands in the region 2000cm−1$2000{\text{cm}}^{-1}$ to 1650cm−1$1650{\text{cm}}^{-1}$ and the positions of the stronger bands in the region 800cm−1$800{\text{cm}}^{-1}$ to 690cm−1$690{\text{cm}}^{-1}$. The sharp bands near 3030cm−1$3030{\text{cm}}^{-1}$ arise from C−H$\text{C}-\text{H}$ stretching vibrations.

          Electronic Absorption Spectra

Compared to straight-chain conjugated polyenes, aromatic compounds have relatively complex absorption spectra with several bands in the ultraviolet region. Benzene and the alkylbenzenes show two bands in which we shall be primarily interested, one near 200nm$200\text{nm}$ and the other near 260nm$260\text{nm}$. The 200$200$-nm$\text{nm}$ band is of fairly high intensity and corresponds to excitation of a π$\pi$ electron of the conjugated system to a π∗${\pi }^{\ast }$ orbital (i.e., a π→π8∗$\pi \to {\pi }^8\ast$ transition). The excited state has significant contributions from dipolar structures such as 1$1$:

This is analogous to the absorption bands of conjugated dienes except that the wavelength of absorption of benzenes is shorter. In fact, the 200$200$-nm$\text{nm}$ absorptions of benzene and the alkylbenzenes are just beyond the range of most commercial quartz spectrometers. However, these absorptions (which we say arise from the benzene chromophore2${}^2$) are intensified and shifted to longer wavelengths when the conjugated system is extended by replacement of the ring hydrogens by unsaturated groups (e.g., −CH=CH2$-\text{CH}={\text{CH}}_2^{}$, −C≡CH$-\text{C}\equiv \text{CH}$, −CH=O$-\text{CH}=\text{O}$, and −C≡N$-\text{C}\equiv \text{N}$; see Table 22-2). The delocalized π$\pi$-electron system of the absorbing chromophore now includes the electrons of the unsaturated substituent as well as those of the ring. In the specific case of ethenylbenzene the excited state is a hybrid structure composite of 2a$2a$ and 2b$2b$ and other related dipolar structures:

Table 22-2: Effect of Conjugation on Electronic Absorption by the Benzene Chromophore

Similar effects are observed for benzene derivatives in which the substituent has unshared electron pairs that can be conjugated with the benzene ring (e.g., −NH2$-{\text{NH}}_2^{}$, −OH$-\text{OH}$, −Cl$-\text{Cl}$). An unshared electron pair is to some extent delocalized to become a part of the aromatic π$\pi$-electron system in both the ground and excited states, but more importantly in the excited state. This is illustrated for benzenamine (aniline) by the following structures, which contribute to the hybrid structure:

The data of Table 22-3 show the effect on the benzene chromophore of this type of substituent - the substituent often being called an auxochrome.2${}^2$ This term means that, although the substituent itself is not responsible for the absorption band, it shifts the absorption of the chromophoric group, in this case the benzene ring, toward longer wavelengths. The auxochromic groups usually increase the intensity of the absorption also.

Table 22-3: Effect of Auxochromic Substituents on Electronic Absorption by the Benzene Chromophore

The benzene chromophore itself gives rise to a second band at longer wavelengths. This band, shown for benzene in Figure 22-3, is of relatively low intensity and is found under high resolution to be a composite of several narrow peaks. It appears to be characteristic of aromatic hydrocarbons because no analogous band is found in the spectra of conjugated acyclic polyenes. For this reason it often is called the benzenoid band. The position and intensity of this band, like the one at shorter wavelengths, is affected by the nature of the ring substituents, particularly by those that extend the conjugated system, as may be seen from the date in Table 22-4.

Figure 22-3: Ultraviolet absorption spectrum of benzene (in cyclohexane) showing the "benzenoid" band.

Table 22-4: Effects of Structure on Electronic Absorption Corresponding to the Benzenoid Band

The benzenoid band corresponds to a low-energy π→π∗$\pi \to {\pi }^{\ast }$ transition of the benzene molecules. The absorption intensity is weak because the π∗${\pi }^{\ast }$ state involved has the same electronic symmetry as the ground state of benzene, and transitions between symmetrical states usually are forbidden. The transitions are observed in this case only because the vibrations of the ring cause it to be slightly distorted at given instants. In the valence-bond treatment this excited state of benzene is an antibonding state of the π$\pi$ electrons.

The electronic spectra of polynuclear aromatic hydrocarbons such as naphthalene and anthracene, in which aromatic rings are fused together in a linear manner, resemble the spectrum of benzene except that the bands are shifted to longer wavelengths. In fact, with the four linearly connected rings of naphthacene, the benzenoid band is shifted far enough to longer wavelengths to be in the visible region of the spectrum (see Table 22-4). Accordingly, naphthacene is yellow. The next higher member, pentacene, is blue.

Compounds such as phenanthrene, chrysene, and pyrene, in which the aromatic rings are fused in an angular manner, have complex electronic spectra with considerable fine structure. The λmax${\lambda }_{\text{max}}$ values normally are at shorter wavelengths than those of their linear isomers.

 Nuclear Magnetic Resonance Spectra

The chemical shifts of arene protons (6.5ppm$6.5\text{ppm}$ to 8.0ppm$8.0\text{ppm}$) characteristically are toward lower magnetic fields than those of protons attached to ordinary double bonds (4.6ppm$4.6\text{ppm}$ to 6.9ppm$6.9\text{ppm}$). The difference of about 2ppm$2\text{ppm}$ cannot be easily explained because the hydrogens in both types of systems are bonded to carbon through sp2$s{p}^2$-σ$\sigma$ bonds.

At least part of the chemical-shift difference between arene protons and alkene protons is the result of the special property of π$\pi$ electrons in aromatic systems of circulating freely above and below the plane of the carbon nuclei, as shown in Figure 22-4. When a molecule such as benzene is subjected to a magnetic field that has a component perpendicular to the plane of the ring, the electrons circulate around the ring in such a way as to produce a local magnetic dipole in the direction opposite to the applied field. This diamagnetic shielding effect acts to reduce the applied field in the center of the ring. Therefore, if a proton could be located in the center of the ring, the applied field would have to be higher than normal to counteract the local diamagnetic field and bring the proton into resonance. A proton outside the ring is affected in the opposite way (paramagnetic deshielding effect) because, as can be seen from the diagram, such protons are located in the return path of the lines of force associated with the local field and thus are in a field greater than that arising from the external magnet alone. When the plane of the molecule is oriented parallel to the field, the diamagnetic circulation is cut off. As a result, as the molecules tumble over and over in the liquid the component of magnetization perpendicular to the plane of the ring varies rapidly.

Nonetheless, a substantial net paramagnetic effect is experienced by the ring hydrogens. The resonance line positions therefore are shifted to lower magnetic fields.

Figure 22-4: Diagram representing the circulation of the π$\pi$ electrons of an aromatic ring under the influence of an applied magnetic field, H0$H_0$. This diagram corresponds to the same kind of effect as that shown in Figure 9-26. The strength of the induced magnetic field, or dipole, is proportional to the applied field.

Strong evidence in confirmation of the above explanation of the chemical shifts of aromatic hydrogens is provided by a study of the cyclic conjugated polyene [18]annulene, which has hydrogens both "inside" and "outside" the ring:

The inside hydrogens are strongly deshielded, coming at 1.9ppm$1.9\text{ppm}$ upfield from tetramethylsilane, while the outside hydrogens are deshielded and come at 8.8ppm$8.8\text{ppm}$ downfield from TMS. As we shall see, the ring current effect is quite general and constitutes a widely used test for aromatic character in conjugated polyene ring systems.

In general, the spin-spin splittings observed between the five protons of a phenyl group can be extremely complex. An example is afforded by nitrobenzene (Figure 22-5), which has different chemical shifts for its ortho, meta, and para hydrogens and six different spin-spin interaction constants: J23$J_{23}$, J24$J_{24}$, J25$J_{25}$, J26$J_{26}$, J34$J_{34}$, J35$J_{35}$, (the subscripts correspond to position numbers of the protons):

Figure 22-5: Nmr spectrum of nitrobenzene at 60MHz$60\text{MHz}$ with reference to TMS at 0.00ppm$0.00\text{ppm}$.

Such a spectrum is much too complex to be analyzed by any simple procedure. Nonetheless, nuclear magnetic resonance can be useful in assigning structures to aromatic derivatives, particularly in conjunction with integrated line intensities and approximate values of the coupling constants between the ring hydrogens, as shown below:

2${}^2$A chromophore is a grouping of atoms in an organic molecule that gives rise to color, or has the potential of doing so when other groups called auxochromes are present.