Tag Archives: Chemistry

Nobel Prizes: USA far ahead in tally


There is no doubt that USA laps up the talent from all over the world. US leads the tally of Nobel prize winners which were introduced in 1901 and Economics prize introduced in 1968. Since then 585 Nobel prizes have been awarded to 922 winners out of which only 49 are women.
Youngest and oldest

Youngest person to receive the Nobel is Malala Yousafzai who received it at the age of 17 years in 2014. Although she belongs to Pakistan, her country may hardly be happy over her winning it. Oldest Nobel laureate is Leonid Hurwicz of US who received the Nobel in 2004 for economics at the age of 90 years.
Countries at the top of list.
USA:

357 total

Chemistry: 73

Economics: 55

Literature: 12

Peace: 22

Physics: 94

Medicine: 101
U.K.

115 total

Chemistry: 29

Economics: 10

Literature: 9

Peace: 9

Physics: 26

Medicine: 32
Germany

82 total

Chemistry: 29

Economics: 8

Literature: 1

Peace: 4

Physics: 23

Medicine: 17
France

57 total

Chemistry: 8

Economics: 2

Literature: 15

Peace: 8

Physics: 13

Medicine: 11
Sweden

33 total

Chemistry: 5

Economics: 2

Literature: 9

Peace: 5

Physics: 4

Medicine: 8
Major areas of research leading to Nobel 

In physics is particle physics and in chemistry is biochemistry. Research in genetics most hot topic and in economics it is micro economics.
Nobel winners of Indian origin 
Ronald Ross: Medicine 1902

Rabindranath Tagore: Literature 1913

C.V.Raman: Physics in 1930

Hargobind Khurana: Medicine in 1968

Mother Teresa: Peace in 1979

Subramanyan Chandrasekhar: Physics in 1983

Amartya Sen: Economics in 1998

Venkatraman Ramakrishnan: Chemistry in 2009

Kailash Satyarthi: Peace in 2014

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Why lobsters and crabs turn red on cooking

These two Sea foods are mouthwatering and popular all over the world. So much so that fairs are held to celebrate the lobster.  One such festival is held in Rockland, Maine which is attended by thousands.

lobster

When cooked these creatures turn coppery red. Although it is not necessary to become a chemist to become chefs but cooking is a science where chemistry takes place at each step. Some chemicals break down to get converted into edible and easily digestible. Similarly in many foods there are color changes when cooked which is also due to chemical modification of ingredients. Here also, chemistry is occurring.

Normal lobster is of muddy color when alive. But the final color is dependent on the amounts of a pigment called astaxanthin which is also the pigment responsible for the red color of carrots, pink of flamingos, salmon and crabs. This pigment is red in color when free. It’s chemical structure is given below.



due to the ketone and alcohol groups this compound is very active chemically easily binds other chemicals like proteins. pigment is a. powerful antioxidant. Lobsters ingest it keep stress of survival under control has been found be beneficial human beings.

What happens in the lobster is that this pigment binds to the proteins in its skin. Due to this binding, it is forced to change its geometric structure and gets twisted to fit in. Depending on the type of protein it bonds to, there’s either what’s called a bathochromic shift, which turns the pigment blue, or a hyspochromic shift, to yellow. When you’re looking at a lobster, you’re seeing light reflecting through different layers of free and bonded astaxanthin–a lot of colors mixed together, hence the muddy brown.

So the final color is a combination of many colors like red, blue and amount and type  of proteins present in the body of lobster and the age . The muddy color is good for camouflaging from the predator because it becomes indistinguishable from the muddy water.

When the lobster is cooked the proteins are denatured and release the astaxanthin pigment turning the cooked meat into coppery red.

Antoine Laurent Lavoisier: Father of Modern Chemistry

Antoine Lavoisier, son of a wealthy lawyer,  was a social climber, tax collector and widely held to be the founder of modern chemistry. He was born in 1743 and was put to guillotine in 1794 on the charges of selling the adulterated tobacco which was a luxury and was very costly. It came from colonies in South America established by Europeans and employed black people as captives.

Antoine-Laurent Lavoisier and His Wife (Marie-...

He discovered oxygen gas and named it so. Joseph Priestly, English scientist had also discovered this gas but named it “dephlogisticated air“. Both knew that the gas was closely associated with combustion in or around 1774. Priestly even demonstrated the synthesis of the gas by heating the mercury oxide with focused sun rays before Lavoisier when the former was a guest of the latter’s family on a tour to France. After some time of this event, Lavoisier also synthesized oxygen by an entirely different method.

He also demonstrated that water which was considered an element to be made of two elements oxygen and hydrogen. He devised a very brilliant method to split the water into

Chem ical ex pe ri ments in In tro duc tion to...

Chem ical ex pe ri ments in In tro duc tion to Chem istry (Seimi Kaisō). (Photo credit: Wikipedia)

its forming elements. The water was boiled and steam was passed through a coiled pipe made of iron. The box containing the coil was joined to another pipe which was dipped into the water at other end.The steam reacted with iron forming oxide thus subtracting the oxygen from water. Another component, namely Hydrogen, went out and bubbled through water and was collected by displacement above water.

Similarly he showed that air which again was considered an element was in fact a mixture of gases.

He is credited with starting the nomenclature of the elements known during his time. He even put the heat also among the elements list. He is thus responsible for initiating the process of documentation of chemsitry.

His another great achievement was what is now known as Stochiometry in chemistry. It is in a way is conservation of mass. He decomposed the salts of known weight and weighed the products and found that total amount remains the same. This audit of the mass has been responsible for the discovery of new compounds and elements and research chemists regularly make use of the this technique to pinpoint the missing mass.

Such a great scientist met with a very sad end. He was hanged when he was barely 50 years old.

A Soccer Ball and C60 Molecule

Carbon, a small atom with atomic weight of 12 amu and atomic number of 6, is the element on which the life on this planet is based. Carbon atom forms 4 single electron bonds of sp3 configuration and hence can combine with 4 different atoms including carbon atoms. Thus it can form giant or macromolecules often found in nature. Some examples are carbohydrates, hydrocarbons, proteins, lipids and so on.

Buckminster Fuller

Carbon as such exists in two allotropic forms namely diamond and graphite with very different physical properties. While diamond is the hardest material and inert towards chemicals, graphite is active, chemically not inert and conducts electricity with ease and has a structure made of hexagonal sheets separated by electron clouds. There sheets can slip over each other making graphite a lubricant. Scientists has been able to separate these 1 atom thick sheets which have extraordinary properties like many times stronger than steel, easily foldable and superconductor of electricity. These sheets has been named Graphene.

Possibilities do not end here. In the interstellar dust, giant molecules of carbon which are very stable and inert have been detected. One of them is C60 molecule. If it was to be superstable and chemically inert, it should have a closed structure. Smalley and Kroto who were awarded Nobel Prize for the discovery looked towards the domes constructed by Buckminster Fuller outlined above. They called this molecule Buckminsterfullerene in his honor. A soccer ball is known as truncated icosahedron which has 60 vertices, 32 faces: 12 of which are pentagonal and 20 hexagonal. Famous architect Buckminster Fuller constructed biosphere structures which are very stable and energy efficient because a sphere has maximum volume but minimum surface area.

Exceptional Brains

Human beings are endowed with power of thinking. All this is possible due to highly evolved brain. But some of us humans are exceptional. Do they see visions? They can predict the events of future. Following are such incidences from the science field.

Sir P.A.M Dirac is considered as the greatest physicist in Britain after Newton. A stern father made him the man of few words. But this trait turned on an intense internal energy which manifested in the form of beautiful equations when he married Einstein’s relativity with quantum mechanism. On the basis of his research, he envisaged sub atomic particles which have equal and opposite electrical charge and equal mass to particles like electrons. His equations yielded two solutions like quadratic equations. Proof came soon when in a experiment in cloud chamber, a particle, hitherto, unknown was observed following mirror trajectory to the electrons emitted from a radioactive particle. It is clear that in a magnetic field, the particles follow a circular trajectory. So this particle was opposite of electron with equal mass. So his prediction was borne true. This particle is called anti-electron or positron. Soon, it became known that there is antimatter to every type of matter. In fact, now scientists believe that there exist space with antimatter and efforts are on to exploit their potential.

Another such great person was a Russian chemist. His name was Dmitri Ivanovich Mendeleev. At the time when he was on the scene, the concept of atomic number of elements was unknown. Only few elements were known to chemists. The physical parameter which was considered important for distinguishing the elements from each other was atomic weight. He was the first man to arrange the elements in groups based on their properties. His insight of the nature was so great that he left many blank places for elements which were not known then. He gave them names prefixed by eka, dvi and tri added to the element preceding the one with eka prefix. For example, ekaboron was the name of element which occupied next place to Boron. It was later discovered and is called Scandium. He had predicted all the properties of the element to be discovered and they matched almost exactly to the element when discovered. His periodic table is the forerunner of the modern periodic table which has evolved over time and is based on the atomic number concept. It is based on the premise that elements in a group have similar electronic configuration and all the elements fall in periods with elements in group having similar properties but increasing atomic numbers. Each element has an added shell of electrons to the previous one. Incidentally, prefixes eka, dvi and tri have been adapted from Sanskrit and mean one, two and three. This love for Sanskrit is said to be due to the influence from a friend who was a Sanskrit scholar.

Kekule, an organic chemist was another exception. He dreamed dreams about atoms and their arrangement. He did it another way around. To explain the unusual properties of a chemical compound and its strange molecular weight, he was so much involved in the thoughts that he was always lost in the reverie. Even while travelling in bus from his laboratory to his home he was so absorbed in the thoughts of figuring out the formula that will explain the observed properties that he had to be reminded by the conductor about the end of his journey. And one day, he saw a dream in which atoms were dancing. Then heavier of them turned into snakes which were joined to each other as each snake has the tail of other one in his mouth. He woke up and rest of night worked out the formula of the first of the aromatic compounds called Benzene.

Putting the Elements in their Proper Places

Elements are entities of the matter which have different chemical and physical properties. Almost all the elements exist in the form of compounds in which different elements are joined in definite ratios and this ratio is always constant. Water is made up of 2 atoms of hydrogen element and 1 element of oxygen. No matter from where you collect the water, it shall have the same composition.

But notwithstanding the differences, they form groups which are like the siblings. They are similar and dissimilar at the same time meaning that they follow a progression of physical and chemical properties. For example. there are elements which called alkali metals which form hydroxides having high pH solutions in water. Only difference is that pH will be different for hydroxides of different metals.

From the days of alchemy, chemists were fascinated by the elements and trying to group them in such a way that elements closer in nature to one another come in one cluster. It was also observed that by placing the elements in rows and columns, moving along a row, at the end of the row, the next element shall be like the first element of the previous row. They tried to understand why sometimes atoms of different elements have strong affinity for each other whereas other atoms hate each other and have to coerced to react with one another.

On the earth’s surface and subsurface, elements are found in the form of compounds and constitute the minerals. Sand or silica is composed of silicon and oxygen atoms and bauxite is made up from the combination of aluminum, oxygen and hydrogen atoms. The lifetime endeavor of many chemists was divide the elements in groups in such a way that properties of elements adjacent to one another can be predicted by looking at their location. They were trying to place them on the paper with their locations in definite arrangements.

After so much efforts, it was the genius of Dmitri Ivanovich Mendeleev, a 19th Century Russian chemist, who came up with arrangement of 63 elements known in his time based on the periodicity of the properties. In placed them in rows called periods and columns called groups and the periodic table of elements was born. The name periodic indicates the periodicity in the properties of the elements. In his time, the concept of atomic structure of atoms was unknown. No one knew the atomic numbers. But in the end when these concepts became popular, the foundation of the periodic table was put on a more firm bases.

Was it not for the genius of the man that he reserved the place in his table for many elements which were undiscovered yet. Despite the many skeptics, he was proved right again. He was influenced by Bohtlingk, a Sanskrit scholar of Russia who was his friend and was preparing the second edition of his book on the Panini who is known for his grammar of Sanskrit, particularly for his formulation of the 3,959 rules of Sanskrit morphology, syntax and semantics in the grammar known as Ashtadhyayi (अष्टाध्यायी Aṣṭādhyāyī, meaning “eight chapters”), the foundational text of the grammatical branch of the Vedanga, the auxiliary scholarly disciplines of Vedic religion, when he gave the prefixes eka, dvi and tri for unknown elements being 1, 2 and 3 places below known element  in the group of elements. For example “ekaboron” was 1 row below and was ultimately identified as Aluminum and so on.

Although the Periodic Table of the Elements was one of the most fruitful ideas to come out of scientific research in the 19th Century, Mendeleev was never awarded a Nobel Prize for this work, although he came within one vote of it in 1906. The reason cited is that one member of the awarding committee argued, rather eloquently, that Mendeleev’s 1869 work had already been widely accepted as a basic part of chemical knowledge, and had already been put forward by the Italian chemist, Stanislao Cannizzaro.

Dmitri Mendeleev died peacefully during a reading of Jules Verne’s Journey to the North Pole, aged 72 on 20 January, 1907. (This was six years after the Nobel Prizes were first awarded).

Since then, eight elements have been discovered and nearly 30 have been made in the laboratory. Mendeleev has the rare distinction of having an element, that with Atomic Number 101 (Mendelevium), named after him. This synthetic element was obtained by Albert Ghiorso, Glenn T Seaborg and co-workers between 1955 and 1958.

Cyclohexane: A Chemical Chair

Cyclohexane belongs to the category of hydrocarbons called naphthenes. It has a chemical formula of C6H12. Naphthenes are found in crude oil. Most abundant are mono ring compounds of which cyclohexane is the perfect example. In fact, the poly ring naphthenes are found in the high boiling fractions of naphtha and the name seems to have been derived from naphtha. The term Naphthene has become almost redundant except in petroleum industry.The other fractions present in the crude oil are paraffins which are long chain alkanes  with formula CnH2n+1. For example, when n=6, then we have hexane with formula C6H14. High molecular weight paraffins are the main constituents of waxes. Another important category of compounds present in the crude oil is called aromatics. The most celebrated and simplest molecule of the category is Benzene with chemical formula C6H6. The overall properties of crude oil depend on the relative amounts of these fractions.

So, we observe that normal hexane, cyclohexane and benzene have six carbons but number of hydrogen atoms go on decreasing while going from paraffins to aromatics. This indicates that we are progressing towards graphite with the loss of hydrogen atoms. Crude oils derived from the marine sources are lighter in nature meaning they have lesser amounts of waxy paraffins. This helps them to be lighter and survive in under sea hydrostatic pressure. On the other hand, plants in the arid climates have wax on their leaves which helps in the prevention of moisture evaporation and is absolutely necessary for the survival of plants under harsh conditions. Thus the crude derived from terrestrial plants have higher wax content.

Anyway, we come to cyclohexane. The carbon atoms try to have tetrahedral geometry around them when combining to 4 atoms. But this is not possible here. So they settle for a compromise for stability. Cyclohexane twists to have a shape like a chair with alternate carbons in two parallel planes and hydrogen atoms arranged in two directions. They are in positions called axial and equatorial positions with axial hydrogen atoms almost perpendicular to the carbon atoms plane with alternating up and down positions.

How was this structure confirmed? It was confirmed by using the tool called Nuclear Magnetic Resonance (NMR) which is used these days in the medical science under the name of MRI. The protons  (hydrogen atoms) behave like tiny magnets and spin around their axis. As we know from the magnets, when we place a small magnet near a strong magnet, smaller one aligns itself along the axis of stronger magnet. Energy is required to flip it back to its original position. Thus the principle of NMR is that molecules are placed in a powerful magnetic field and swept with electromagnetic energy. This will be of no useful tool if all the hydrogen atoms absorb the energy at same wavelength. Fortunately, the magnetic moments of hydrogen atoms are modified by the electronic environment around it a molecule which may be due to the presence of hetero atoms and groups or different number of groups. Thus due to the different environment, the hydrogen atoms absorb energy at different wavelengths. From this we come to know the chemical environment of different hydrogen atoms and thus elucidate its structure. In our brain, we have so many molecules which contain hydrogen atoms and these are affected by the state of our mind.

When cyclohexane is placed in a NMR cell, we get only a single signal indicating that all the hydrogen atoms are equivalent. But this is true only at normal temperature. The reason is that axial and equatorial hydrogen atoms flip up and down because energy required for this is very small and room temperature provides it. But as we cool the sample, less energy is available and a temperature reaches 40K, the atoms sort of freeze in their locations and two peaks begin to appear. These peaks are indicative of up and down orientation hydrogen atoms. This confirms a chair configuration of cyclohexane.

Achievements of a wandering mind

Many a times you must have experienced in your life that you cannot recall a certain incident, name of a person or a book or author although at other times you remembered it so well. In those circumstances, the harder you try to recall more it eludes you. It is not the case of poor memory or age as it happens with everyone at one time or another. You leave it frustrated and become busy in some other work and in a flash the things will come to your mind. The same has happened to many great scientists and authors.

August Kekulé von Stradonitz, the great chemist who elucidated the structure of benzene did it in reverie while riding a horse drawn bus. As he will doze off, he saw the atoms dancing before his eyes. These atoms caught hold of each other. The bigger ones held more than one smaller atoms and so on. Thus he was able to arrive at the ring structure of the benzene molecule. Not only that, he was able to draw the structure of molecules with same molecular formula but different physical properties. He was talking about geometrical isomers. It was left to his brilliant young student Vant Hoff to discover the sterochemistry of carbon molecules in which for different groups are attached to a carbon atom. Such carbon atoms are said to be asymmetric and stereo isomerism imparts a property of deflecting light to right or left from its path when light travels through the solution of such substances. Such molecules are called optically active compounds with dextro (right) rotatory and levo (left) rotatory categories. Whenever such compounds are synthesized in the laboratory we end up with 50:50 mixtures of both forms which are optically inactive because the deflection caused by one set to left is countered by another set to the right. To separate these mixture into pure forms, these mixtures are reacted with a pure levo or dextro rotatory compound resulting in two salts of different melting of boiling points which are easily separable. After separation the add on moelcule has to be detached to obtain the pure compound of levo or dextro nature. n nature, we encountered only single type of compounds either levo-rotatory or dextro rotatory because most of the natural compounds are synthesized by different routes using the enzymes. It was the great Luis Pasteur who separated the two optically active  forms of tartaric acid crystals using tweezers and demonstrated the optical activity. The weather of France also assisted him because the tartaric acid obtained from the raw grapes formed large beautiful crystals.

Another example of great achievements of wandering mind is that of Greek mathematician Archimedes. He was given the commission by the King to know whether the crown he ordered to be made was really of Gold or of gold alloy. Archimedes thought and thought about solving the problem from many angles but was frustrated and he decided to leave aside the problem for sometimes. He ordered his servant to make a bath for  him. As he lowered himself into the bath, he saw the level of water rising. The idea that same weights of different elements displace the different volume of water suddenly flashed to his mind. This way he can find the volume that a certain weight of gold will occupy perhaps by comparing the crown weight by same weight pure gold. He was so elated that he jumped out of the bath and ran naked towards the palace shouting the now famous word  “Eureka”

Tri-Phenyl Methyl: The Radical which can be bottled

Most of the reactions in the organic chemistry the formation of short lived radicals or carbonium ions. They are the highly reactive. Element Carbon, the element about which the whole branch of organic chemistry revolves, has 4 valency and thus forms 4 single covalent bonds. It has got 4 unpaired electrons in the sp3 configuration which means that 4 equivalent hybrid orbitals are formed by combination of 1s and three 3p orbitals in the second shell.

During many reactions, one unpaired electrons remains when 1 atom attached to carbon is ripped off. This is of the form R3C. where R are alkyl groups. This is a radical and is extremely reactive and seeks to stabilize itself by combining with another atom with 1 unpaired electron. These radicals thus live for very short time during the steps of organic reactions. Sometimes their existence seems to be a fable.

But then, there was a very brilliant Russian organic chemist. His name was Gomberg. Still a student, he wanted to substitute all the hydrogen atoms on the methane and ethane with bulky C6H5 phenyl groups. No one had done this before. He did many experiments and after excluding oxygen from his experiments he was able to prepare the first stable radicals ever found in organic chemistry.

This was tri-phenyl methyl radical. Its solution when oxygen was blanketed have slightly yellow color which intensified upon warming. As we have said that radicals try to combine with other atoms with unpaired electrons. The trick is to become stabilized and have lowest energy. They are sitting on the top of potential energy high called transition state in chemistry. Here come the phenyl groups which share their electrons to stabilize the radical. Phenyl rings have a cloud of 6 pi electrons and they begin to disperse and stabilize the unpaired electron on the carbon be transporting the electron into the clouds especially on ortho and para positions. Since there are 3 phenyl rings, the dispersal of the unpaired electron is very large and thus the radical becomes stabilized. Also such molecules and radicals absorb light in the visible spectrum of light. Since it looks yellow in color, it means it absorbs the light in the lower part of spectrum leaving the yellow light for transmission.

When these solutions are exposed to oxygen which is famous for breaking into free radicals then the color begins to disappear and stable compounds are formed by reaction of 2 tri-phenyl methyl radical with one oxygen atom and is colorless.

We must appreciate the fact that in those times when not many of the analytical instruments were available, these chemists with their logic and classical compositional analysis were able to achieve so much insight. This is why the chemistry is called a fundamental science. Without it no field like geology, physics, biology, genetics and other modern science can progress. We must also give the due credit to Russian scientists whose works remained obscure in the era of communism when even the science discoveries were under the whip of communism.

For more details and diagrams please visit this page on wikipedia which is doing a great service to the world by imparting and dissemination of knowledge.

Dream of Kekule:Benzene

Continuing the subject of dreams, it is pertinent to mention that lucid dreams had helped many to make great discoveries and inventions. Since my subject is chemistry, I will touch upon one such famous dream which laid the foundation for understanding the structure and chemistry of  aromatic compounds.

As every one versed with chemistry knows, the benzene is the starting compound of aromatic compounds. Its structure was derived by Kukule’. His full name was Friedrich August Kekulé von Stradonitz.

kekule-benzene-stamp

Benzene was analyzed to have 6 carbon and 6 hydrogen atoms. Existing formula of all the organic compounds did not fit into the structure of benzene and explain its strange properties.

Kukule’ was working on this problem but could not find its solution. Totally engrossed, he fell into a sleep in front of fireplace. He has a dream of the atoms which he described in his own words as follows:

“…I was sitting writing on my textbook, but the work did not progress; my thoughts were elsewhere. I turned my chair to the fire and dozed. Again the atoms were gamboling before my eyes. This time the smaller groups kept modestly in the background. My mental eye, rendered more acute by the repeated visions of the kind, could now distinguish larger structures of manifold conformation; long rows sometimes more closely fitted together all twining and twisting in snake-like motion. But look! What was that? One of the snakes had seized hold of its own tail, and the form whirled mockingly before my eyes. As if by a flash of lightning I awoke; and this time also I spent the rest of the night in working out the consequences of the hypothesis.”

So the snake he saw holding its own tail in its mouth was the the circular structure or closed ring structure of benzene. He immediately woke up and worked out his dream on the paper and by morning he had discovered the chemical structure of benzene.

snake

From the chemical point, the formula of benzene is C6H6. Kekule proposed the following structure to explain the number of substitution compounds which have been synthesized  using this structure.

Kekule's Benzene

Still there were problems in explaining the two different compounds obtained when hydrogen atoms on adjacent carbons were substituted with two different radicals like cl, NO3, I or CxHy. This is called ortho disubstituion. That is to say that C6H4XY will form two different ortho isomers depending  on whethere substitution has taken place C-C bond or C=C bond.  But such isomers have never been found. Kekule tried to explain this by saying that single and double bonds oscillate and thus become identical. Dr.Linus Pauling later on proposed resonance phenomenon, in which there are no purely single and double bonds but something in between and thus all C-C bonds are equivalent. This has been conformed by UV analysis which shows all C-C bonds of equal strength and indistinguishable. This is like the Hindu God Shiva when He assumed ardhnarishwar or androgynous form to show that both male and female forms coexist in the body. The final outcome depends upon which of these dominate at a given time.

In the end of a lecture explaining the discovery of benzene, he said

“Let us learn to dream!”