Visions of the Cosmos

Life Among the Stars

Through the Looking Glass.  The Life of a Chemical Genius: Henri van't Hoff

Introduction

 Jacobus Henricus van't Hoff was born on 30 August 1852 in the small town of Sommelsdijk near Rotterdam. He grew up to be a person of outstanding genius and during his life made many revolutionary discoveries in the field of chemistry. At the early age of 22, he opened a door to a mirror world and solved a problem in chemistry that had been puzzling many talented minds of the day for several years.  This was only the beginning of a brilliant career, which was to lead to many other fundamental contributions to science, and was to culminate in the award of the very first Nobel Prize in Chemistry in the year 1901.  He was born eight months before that other famous Dutchman Vincent van Gogh. It is perhaps a commentary on our false sense of values that almost everyone knows about the artist, whereas few people outside scientific circles will have heard of Jacobus Henricus van't Hoff.

Early Years

Henri as he was usually called, was his parent's eldest surviving child.  His elder brother and sister died in early childhood.  Four brothers and one sister survived into adulthood. By all accounts, he had a very happy childhood.  His father was the local doctor and a respected member of the community.  His mother and father provided a stimulating intellectual atmosphere.  They had a great passion for the works of William Shakespeare, which they passed on to their children. The family was quite a large one and each member was provided with a copy of the relevant book.  All the children would sit together with their parents at the table in the evenings and read the plays of the famous bard.  This introduction to English literature led to Henri's early infatuation with the poems of Lord Byron and his deep admiration for the Scottish poet Robert Burns.  Henri often went on holiday to stay with his grandparents.  The small town, in which they lived, was set in beautiful surroundings made famous by the eighteenth century artist Hobbema whose painting ' An Avenue in Middleharnis' now hangs in the London National Gallery.   

At an early age, Henri became captivated by the science of Chemistry. As a teenager, he would entertain his parents and their friends with demonstrations of chemical reactions and glass blowing.  As a reward, they would give him pocket money to buy more materials and equipment for his home laboratory.  At the age of 17 he matriculated from the University of Leiden and then went on to the Delft Polytechnic School.  He was a very serious young man and did not involve himself in the more light hearted and frivolous aspects of student life but immersed himself in hard work.

He continued his studies at Bonn, which was, at the time, one of the most illustrious seats of learning in the world.  He was very happy there and wrote enthusiastic letters to his father in which he described the university as a temple. He was one of a hundred of the world's most brilliant young people from ten different countries who flocked to Bonn to sit at the feet of the charismatic Professor August Kekulé.   Kekulé was an extremely gifted teacher who became famous for his discovery of the ring structure of benzene and his extensive researches into aromatic chemistry. One event, however, clouded van't Hoff's time in Bonn. The news of the suicide of a young woman student who had killed herself by drinking potassium cyanide solution shocked everyone at the University.  His response to the tragedy showed him to be a young man of deep sensitivity. On hearing of her death, the young Henri immediately wrote a long poem in English, in the style of Byron, entitled  'Elegy on the Death of a Lady Student at Bonn'. 

In early 1874, after two years in the Rhineland, van't Hoff went to study for a short while in the Paris laboratories of Professor Charles-Adolphe Wurtz. He did not stay long in Paris, however, since his parents were impatient for him to finalise his university studies by acquiring a doctorate.  Accordingly, he returned to Holland with excellent testimonials from both Kekulé and Wurtz.  In December of that year, he was awarded his doctors degree from the University of Utrecht. Following this he was appointed to the post of Assistant Lecturer in the Utrecht Veterinary College where he taught physics.

 Entry into the Mirror World - Chemistry through the Looking Glass

In September 1874, before he even obtained his doctors degree, van't Hoff wrote an eleven-page dissertation in his native language about the arrangement of atoms in space.    It was fortunate that he published when he did; two months later in November of that same year Joseph Achille Le Bel, gave a lecture to the French Chemical Society, on almost the same subject. Coincidentally the two young men had met in Paris only a few months earlier.  However, they never discussed the ideas, which were to make them so justly famous. To them both, must go the honour of discovering one of the most important and fundamental facts of science concerning the structure of organic molecules.

Whilst van't Hoff was still a young child, Louis Pasteur was actively engaged in the study of simple organic molecules which appeared to exist in three forms.  In particular he carried out work on the salts of tartaric acid. Pasteur made two important discoveries with respect to tartaric acid and its salts.

He found that that if he recrystallised sodium ammonium tartrate from concentrated solution below 28 degrees Celsius he obtained two kinds of crystals.   Working carefully with a pair of tweezers, he separated the crystals into two piles.  He found that they were mirror images of one another (see Figure 1).

He dissolved each pile of crystals in water.  He tested each solution in an apparatus called a polarimeter and found that the solutions were optically active; they rotated the plane of polarised light to the same extent but in opposite directions. On the other hand, the original solution did not rotate the plane of polarised light at all. He found that if the original (optically inactive) solution was fermented in a vat with yeast only one form reacted leaving the other behind unchanged. He also discovered that on incubating the optically active solutions separately with wine yeast only one of the two forms underwent fermentation.  It now became obvious that the original substance was in fact a mixture of equal quantities of the two optically active forms.

 Following the discoveries of Louis Pasteur several other chemists carried out extensive work on other organic compounds of biological interest.  In particular Professor Johannes Wislicenus, at his laboratory in Wurzburg, carried out experiments on the lactic acids.  He found that, like tartaric acid, lactic acid existed in two optically active forms.   It soon became apparent that most, but not all compounds, which were involved in biochemical processes, existed in two forms.  In most respects, they were chemically similar.  It was however found that in general only one of them was biologically active. It took the scientific world many years to discover the true nature of the phenomenon, which is called stereoisomerism or optical isomerism.   It was not until van't Hoff and Le Bel independently offered an explanation that the true reason for the existence of pairs of optical isomers was satisfactorily explained.

In 1875, van't Hoff published a version of his paper in French entitled 'La chemie dans l'espace'.   The young chemist was highly supported by Wislicenus at whose instigation the thesis was translated into German by one of his former students, F.Hermann.   Many members of the scientific establishment, however, were either very sceptical or even openly hostile to the new ideas.  In particular Professor Kolbe of Leipzig University was personally abusive.  He is quoted as having stated 'A Dr van't Hoff of the Veterinary College, Utrecht appears to have no taste for exact chemical research.  He finds it a less arduous task to weave fantasies.  His hallucinations have met with but little encouragement from the chemical public'. Kolbe was equally vitriolic towards the supporters of van't Hoff's ideas.  He wrote, 'Dr F.Hermann, of the Agricultural Institute of Heidelberg, undertook to give these fantasies further publicity by publishing a German edition.  It is impossible to criticise this paper since its fanciful nonsense is quite unintelligible to the calm investigator.'  Likewise he attacked Professor Wislicenus; ' Wislicenus makes it clear that he has gone over from the camp of the true investigators to that of the speculative philosophers of ominous memory, who are separated by only a thin medium from spiritualism.'

Van't Hoff and Le Bel had discovered the simple fact that if a carbon atom is connected by four single covalent bonds to four different atoms or groups of atoms A, B, C, and D then two different arrangements in space are possible.  This results in the existence of two isomers which are mirror images of one another.

In one fell swoop; the discovery made by the two young men had revolutionised organic chemistry.  It was not long before Kolbe and their other detractors were proved utterly wrong.

In particular van't Hoff developed the idea of the tetrahedral carbon atom.  He postulated that the four valencies of a carbon atom are directed towards the corners of a tetrahedron with the carbon atom its centre.  By introducing the concept of 'the asymmetric carbon atom' combined with four different groups, he gave a satisfying explanation for the existence of numerous pairs of optical isomers. Strictly speaking, it is not the carbon atom that is asymmetric but the structure of the whole molecule.  It is now the custom to speak of 'chiral molecules' from the Greek word meaning hand.  Thus, we have 'right-handed' and 'left-handed' molecules.  

 The really great interest to modern molecular biologists is the fact that amino acids, sugars and the components, which make up the genetic material DNA, show 'handedness'. The presence of amino acids has now been detected in meteorites (the Murchison meteorites).  Although both isomers are present, the 'left-handed' variety predominates. A sample of the amino acid alanine from the meteorite showed a high 13C/14C ratio thus indicating its extra-terrestrial origin.  This has proved that amino acids can originate outside the Earth.  Suggestions have been advanced that in its early history our planet may have been 'seeded' by organic molecules contained in meteorites and comets.

On Earth, only L-amino acids are used to build up proteins.  There seems to be no special reason why one form should be preferred over the other.  Recent work in astronomy suggests that some regions of space are subjected to polarised radiation emanating from neutron stars some of which is circularly polarised clockwise and some anticlockwise.      Moreover, chemical experiments show that the decomposition and the synthesis of optically active substances are affected by the radiation in the environment in such a way that the amount of one form is favoured over the other. This would suggest that there might well be biochemical systems on other planets where only the D-forms are used in the synthesis of proteins.  The fate of a hypothetical earthman or woman, after travelling through a wormhole to such a mirror world, would indeed be a sad one.  However good the food seemed to be they would soon die of starvation since the mirror image 'food' would be of no use whatsoever!  There is no doubt that were he alive to-day these ideas would fascinate van't Hoff.  How intrigued that young man of 22 would have been had he realised the full significance of his discovery and by the advances that have been made since his day in biochemistry and astronomy.

 

The three figures shown below all illustrate the three dimensional structure of right-handed and left-handed alanine.

  

 


 

 

 

The Amsterdam Years 

In 1878, at the early age of 26, van't Hoff was appointed by the unanimous acclaim of the faculty to the Chair of Chemistry, Mineralogy and Geology at the University of Amsterdam. He taught chemistry, crystallography, mineralogy and palaeontology to graduate and undergraduate students in chemistry and in medicine. 

There can be little doubt that during his eighteen years in Amsterdam van't Hoff was considerably overworked.  Not only did he have a heavy teaching and administrative load but he also busied himself with many research projects.

Apart from his professional duties, he also took on the responsibilities of a family.  Shortly after his appointment to the post at Amsterdam, he married his childhood sweetheart Johanna Francina Mees, the daughter of a Rotterdam merchant.  They had two daughters and two sons.

During the 1880s van't Hoff was deeply involved in carrying out research into the rates of chemical reactions and into the properties of substances in solution.  In 1884, he published a book in French entitled 'Etudes de dynamique chimique'. In the following year, he submitted a paper to the Swedish Academy of Sciences on the laws of chemical equilibrium in the gaseous state and in dilute aqueous solutions.   His ideas met with little attention from the scientific world except from Wilhelm Ostwald in Riga and a young, then almost unknown chemist in far off Sweden. It was none other than Svante Arrhenius who was later to become, with Wilhelm Ostwald and van't Hoff himself, one of the most brilliant physical chemists at the turn of the century. This led to deep and abiding friendships between the three men.  In 1887 van't Hoff and Ostwald began the publication of a new and important journal the 'Zeitschrift für physikalische Chemie, Stoichiometrie und Verwandschaftslehre' to help publicise the new ideas.

            During the 1880s and 1890s van't Hoff and Arrhenius were busily involved in their work on solutions.  Together they laid the foundations of our understanding of how substances behave in dilute aqueous solutions.   Their discoveries are of supreme importance in  understanding the way in which biological system function. 

The Berlin Years

Such was the reputation of van't Hoff that many authorities wanted to employ his services.  In 1894 the University of Berlin offered him the vacant chair in experimental physics.   Two very eminent scientists of the day Max Planck and Emil Fischer made every effort to persuade him to accept the offer but at first with no success. He was very attached to Amsterdam and, after agonising discussions with his father, he initially turned down the offer of the post at Berlin.  However, his job in Amsterdam was extremely demanding and the Berlin offer was still very tempting.  Moreover, Berlin badly wanted van't Hoff and they made him more and more tempting offers. He was able to negotiate a much lighter workload.  At  last, he agreed to go to Berlin almost on his own terms and in 1896, he took up his new post. He wrote to his friend Ernst Cohen  'This is quite a new life and I look forward with hope to the future.  Our apartment here is excellent and the situation all that can be desired.  A pleasant walk takes us to the nearby forest of Grunenwald from where we can return by train if we wish.  I now find much more time to be with my family.'     This shows that he had begun a new and more relaxed life.  Nevertheless, he was still extremely active and bent his energies in many directions.  Chief among these was a detailed study of the large mineral deposits at Stassfurt.  During the Permian Period, 250 million years ago, a vast inland sea, known to geologists as the Zechstein Sea, was slowly drying up.   It acted like a huge evaporating basin and vast salt deposits were left behind. Where these outcropped at such places as Stassfurt in Germany, it was possible to mine the mineral salts deposited.  Van't Hoff made an extensive study of these deposits and his contribution to the German Potash Industry was incalculable.   

During his life van't Hoff travelled widely over Europe and North America.

His greatest triumph came in 1901when he travelled to Stockholm to receive the very first Nobel Prize in Chemistry. In the same year, he undertook a long visit to America to attend the tenth anniversary of the founding of the University of Chicago. With his wife by his side, he was treated like a king.  On the voyager over the Atlantic, the directors of the Holland-America line set aside a stateroom for his wife and himself and they dined at the Captain's table. Whilst in America he not only visited Chicago but was also welcomed in Yale, Harvard, Cornell and Woods Hole.

 In 1903, he attended the centenary celebrations of Dalton's Atomic Theory at Manchester.  At the entrance to the chemical laboratory of the University there is a tablet inscribed ' This stone was laid by Professor J.H.van't Hoff, 20 May 1903, in commemoration of the centenary of Dalton's Atomic theory.' 

In 1904, he represented the German Chemical Society at the seventieth birthday of Adolph von Baeyer who, as far back as 1875, had supported the young man's contribution to stereochemistry.

In 1906, he attended a conference of Austrian engineers and architects in Vienna where he delivered an address on thermochemistry.  In the same year he and his wife went to Italy where he studied the volcanic activity of Vesuvius which was in eruption.  During the trip his lungs became weakened by the inhalation of volcanic fumes and dust.  It is possible that this may have been a contributory cause of the tuberculosis which he contracted around this time.

 Sadly, the last few years of van't Hoff's life were wracked by ill health.  He suffered from bad hay fever and worse he had contracted tuberculosis, which grew steadily worse. He died on 1 March 1911.  He was cremated and his ashes rest in the cemetery of Berlin-Dahlem.

In 1906, he attended a conference of Austrian engineers and architects in Vienna where he delivered an address on thermochemistry.  In the same year he and his wife went to Italy where he studied the volcanic activity of Vesuvius which was in eruption.  During the trip his lungs became weakened by the inhalation of volcanic fumes and dust.  It is possible that this may have been a contributory cause of the tuberculosis which he contracted around this time.

 Sadly, the last few years of van't Hoff's life were wracked by ill health.  He suffered from bad hay fever and worse he had contracted tuberculosis, which grew steadily worse. He died on 1 March 1911.  He was cremated and his ashes rest in the cemetery of Berlin-Dahlem.

During his life, van't Hoff received many honours.  He has moreover left a lasting and indelible impression on history.  Every student of chemistry who learns about osmotic pressure and about optical isomerism must come across the name of this intellectual giant.  Perhaps one day if we ever contact some of those other 'people' who share with us the stars we may find that on a distant planet orbiting some alien Sun their bodies are made of right-handed amino acids.  Perhaps if that day ever dawns our successors may remember the name of van't Hoff whose discovery of optical isomerism at the young age of 22 gave us the clue to the existence of a mirror world.

References

1       Ernst Cohen:  *Jacobus Henricus van't Hoff, sein Leben und Wirken * Akademische Verlagsgesellschaft 1912, pp 628-629

2       August Comte * Cours de philosophie positive*  La Librarie Scientifique-Industrielle 45 Quai Malaquais, Paris  1851

3       Ernst Cohen * Jacobus Henricus van't Hoff, sein Leben und Wirken*  Akademische Verlagsgesellschaft   1912  Copy of complete elergy

Benjamin Harrow  *Eminent Chemists of our Time *  1920 Van Nostrand, New York and Fisher Unwin, London  1920 and 1921  page 84 first verse of elergy

4       J.H.van't Hoff.  * Vorstel tot uitbreding der tegen woordig in de scheikunde gebruikte structuurformels in de ruimte, benevens een daamee samenhangende opmerking omtrent het verband tusschen optisch actief vermogen en chemische Constitutie van organische verbindingen *   Utrecht J.Greven  5 Sept 1874                   

5         J.H.Van't Hoff   * La chemie dans l'espace *  P.M.Bazendijk Rotterdam  1875

6       Dr F.Hermann  *Die Lagerung der Atome im Raume mit einem Vorwort von Johannes Wislicenus *  Vieweg und Sohn Braunschweig  1877      

7        Benjamin Harrow *Eminent Chemists of our Time *Van Nostrand, New York and Fisher Unwin, London  1920 and 1921  pp 87-88

8        Van't Hoff J.H. * Etudes de dynamique chimique * Amsterdam Frederik Muller and   Co  1884

9        Benjamin Harrow  *Eminent Chemists of our Time * Van Nostrand, New York and Fisher Unwin, London  1920 and 1921  page 95 regarding letter of 25 April 1896 from van't Hoff to Ernst Cohen.

10                 Ernst Cohen:  *Jacobus Henricus van't Hoff, sein Leben und Wirken * Akademische Verlagsgesellschaft 1912, pp 628-629

11                 August Comte * Cours de philosophie positive*  La Librarie Scientifique-Industrielle 45 Quai Malaquais, Paris  1851

12                 Ernst Cohen * Jacobus Henricus van't Hoff, sein Leben und Wirken*  Akademische Verlagsgesellschaft   1912  Copy of complete elergy

Benjamin Harrow  *Eminent Chemists of our Time *  1920 Van Nostrand, New York and Fisher Unwin, London  1920 and 1921  page 84 first verse of elergy

13                 J.H.van't Hoff.  * Vorstel tot uitbreding der tegen woordig in de scheikunde gebruikte structuurformels in de ruimte, benevens een daamee samenhangende opmerking omtrent het verband tusschen optisch actief vermogen en chemische Constitutie van organische verbindingen *   Utrecht J.Greven  5 Sept 1874                   

14                 J.H.Van't Hoff   * La chemie dans l'espace *  P.M.Bazendijk Rotterdam  1875

15                  Dr F.Hermann  *Die Lagerung der Atome im Raume mit einem Vorwort von Johannes Wislicenus *  Vieweg und Sohn Braunschweig  1877      

16                 Benjamin Harrow *Eminent Chemists of our Time *  Van Nostrand, New York and Fisher Unwin, London  1920 and 1921  pp 87-88

17                 Van't Hoff J.H. * Etudes de dynamique chimique * Amsterdam Frederik Muller and   Co  1884

18                 Benjamin Harrow  *Eminent Chemists of our Time * Van Nostrand, New York and Fisher Unwin, London  1920 and 1921  page 95 regarding letter of 25 April 1896 from van't Hoff to Ernst Cohen.

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