Chemistry 11 Hand In Assignment # 14 Chemical Bonding Name Date Due Date Mark 54 Co: Fill & Download for Free

Remove the minimum 75% attendance criteria. First and foremost.Upgrade systems and equipments in labs. I am a computer engineering student, and when everyone is bringing their own laptops, you know labs have problem.Bring back the original student intake. Reduce the seats. I am not against more students getting admission, but currently university is not ready for it. If you no longer find a place to sit in library or canteen or anywhere else, there's a problem.Construction of more hostels and classrooms, even if it requires this “forest area” to be cleared. Advertisement of “lush green campus” is not that cool when your lab subjects have no lab taking place, because all labs are full. (see point 3)This one is controversial, but remove reservation, for students admission and teacher’s recruitment.Removing handwritten assignments and lab files, especially, when you run the code, take its output, then write the code in file and paste the screenshot. Seriously ^_^ Also, if we have run the code, why is its hard copy needed to check it? Do you not trust our laptops? Are they not running correctly?Starting with core engineering subjects in first year itself instead of studying Physics, Chemistry etc.Changing to 50 theory 50 practical instead of 70 theory 30 practical weightage.( Provided next point is also applied. )Revising the whole syllabus once, and making syllabus more industry oriented and practical based. If there are coding coaching institutes thriving alongside engineering colleges, there's a problem. If a company hires a 8.5 GPA student over 9.8 GPA, there’s something wrong with system which is giving GPA. Shouldn't it be better performance in engineering college means more employable engineer.Again controversial one. Teachers could be recruited on criteria of how well they deliver or present the knowledge as compared to how knowledgeable they are? Even PhDs or post doctorates struggle to explain a PowerPoint presentation. We would prefer B. Tech who have good grasp over communication skills. (Even, knowledge is not proportional to degree :p)Checks could be made that syllabus and teachers are regularly installing their updates. Long story short, we have a subject “Professional Ethics and Human Values”, whose teacher tells in class how lovers holding hands in restaurant is unethical. (Thank God, he didn't say girls should cover their faces in class :p) He is recently recruited faculty.That's enough ranting for today :)

Disclaimer: It is not about marketing and none of the content mentioned is exaggerated.When you meet him for the first time, you feel “Abbey kya ajeeb aadmi h!? ‘ullu ka pattha, gadha, lallu, amma aur saala jaise words use krta h. Ise kon jhelega poora saal! Ye aadmi to chemistry se air zada nafrat karayega!”. But as time passed I realised that I was so wrong!.I am a VMC Pitampura pass-out. I really wanted to get into the IITs but due to some reasons, I joined coaching for class 12th. And I chose VMC or better to be put this way, VMC selected me. The one year batch was a new experience for the VMC squad, and hence we were assigned senior teachers, the teachers who taught two year, three year, four year program students, the students who were desired for the two digit ranks they'd fetch. The challenge was this: completing the syllabus of 11 & 12 both in a course of mere ten months. To be more clear, it meant 30 significant chapters of chemistry (when I say ‘significant’, I mean chapters which had an upper hand in concepts;there were more of course), 20 significant mathematics and 18 physics. How can a good student, but a student who has no experience of this race, would be able to make both the ends meet? How can you rebuild the tempo of two years in 10 months? The other two teachers felt this way. Some of us did too. They were like “ barhwi to krlo, gyarhwi to dekhi jaayegi”. But Rahul bhaiya was different. He never said that, he always had plans. And those plans were not like the flop 31st December plans we friends make. He made benchmarks, helped us, motivated us, but not by lying, but by making us realise that what were we doing to ourselves and most importantly our parents. He made students feel guilty, he made some of us cry at times. He changed lives. He still is working for the same. He completed the syllabus, made us revise it, taught that chemistry has all the logics ; it's the teachers who lie to us about the logics. Every reaction in inorganic had a logic; he explained it righteously. Every organic reaction had a mechanism which is determined by the electronic effects and a lot of other factors. He made me realise why chemistry is not mugging up things, it's much more. He cleared all kind of problems (emotional, intellectual, spiritual and what not!) of all the kids. He didn't make me an IITian. But he made me strong. He is the only human comparable to God (no exaggeration folks!)I didn't become an IITian, but I became a fighter, I would've lost faith in myself without him. I would've felt like a loser all my life. But I don't. There are people who hate him because of the extra stuff he teaches. But they all are fools. I remember the last class of VMC, it was 11.05.2017 was Rahul bhaiya's class and he quoted : “extraordinary zindagi ram ji sab ko nahi dete, na sabko mil skti h, pr ek extraordinary thinking hr koi rkh skta h. IITian bnke shahi paneer khake bhi insan to kharab ho skte ho. Maa baap puchhenge bhi nhi us paneer ko jo ek nalayak aulad ka h. Sanskari bno, sukhi roti bhi shahi panel se zada sukoon degi.”And when it comes to describing him on overall bases, Rahul bhaiya is a game changer, a table Turner, sarcastic, funny, a genius, modest teacher. An amazing story teller, a loving and caring elder brother. He is my personified God.Jai Shree Ram

For the general public the name of Louis Pasteur goes hand in hand with the pasteurization of milk. He also created the first vaccines for rabies and anthrax and is considered as one of the fathers of microbiology. However we chemists claim him as one of us. Since he is responsible for one of the most important chemical breakthroughs in history. It's in the same category as Kekulé’s benzene representation or Haber’s ammonia process.Figure 1: Louis PASTEUR | Académie françaiseIn order to unravel his discovery we need to go back to the early 19th century.I. INTRODUCTION - Rotation of lightScientists just discovered that some quartz crystals rotated plane-polarized light. More complete, some of the crystals rotated the light to the right, some to the left. It was Herschel that linked this feature to the orientation of the so-called hemihedral faces of the crystals. [1]Crystals can be homohedral or hemihedral; hemihedral refers to:having only half the planes or faces required by the maximum symmetry of the system’.But my brain is too small to truly understand that definition. So I added a picture of the optical active quartz crystals: the small white surfaces, replacing half of the corners of the crystal: those are the hemihedral faces.Figure 2: Left Handed and Right-handed Quartz crystals -Prelog (1976) (© The Nobel Foundation.)They also discovered that some organic products did the same in solution. (e.g. Laurel Essential Oil turns the light to the right, lemon oil to the left.) [2]It was a bit of a mystery why organic molecules did that in solution but the same compound (most of the time) didn't in crystallized form and that Quartz had just the opposite behaviour: i.e. molten quartz was inactive [3]One of the organic molecules that puzzled chemists was tartaric acid: the compound isolated from ‘cream of tartar’. Cream of tartar might be meaningless for most of you, but the Dutch and German names of this product, respectively Wijnsteenzuur and Weinsteinsäure (or ‘wine stone acid’) are more comprehensible. Indeed ‘tartar’ or wine lees is the residue that forms during fermentation of grapes and it consists of the monopotassium salt of the acid.When you heat tartaric acid a different compound can be isolated. Gay-Lussac coined this new product racemic acid (d’acide racémique, from racemus, Latin for bunch of grapes.) Berzelius another famous chemist used a different name: he called it paratartaric acid [4]and found that the compound had the same atomic weight and the same empirical formula as tartaric acid. (It is Berzelius that introduced the name isomer from the Greek, ἰσομερής, isos = "equal", méros = "part") In this context: racemic acid was an isomer of tartaric acid. Racemic and tartaric acid had almost the same properties. It had the same melting point and the same solubility properties, virtually everything was the same. The only differences were related to the crystal forms of the salts and that only tartaric acid rotated polarized light, racemic acid was optically inactive.[5]II. PASTEUR’s DISCOVERYPasteur stumbled on his discovery by accident. As a young researcher he wanted acquire some knowledge of crystal structures and he thought it would be a good idea to repeat the work of De la Provostaye [6] on the various salts of tartaric acid and racemic acid. During this work he discovered that all salts of tartaric acid formed hemihedral crystals and even more remarkably all in the same sense. The racemates however were all homohedral. Inspired by Hershils work [1]on the quartz crystals, Pasteur postulated that there must be a relation. When he was reading in the library of Paris, he noticed an article [7] stating that one particular racemate salt was not homohedral. This was in contradiction with his own observation. But let's use Pasteur's own words [8]I hastened therefore to re-investigate the crystalline form of Mitscherlich's two salts. I found, as a matter of fact, that the tartrate was hemihedral, like all the other tartrates which I had previously studied, but, strange to say, the paratartrate was hemihedral also. Only, the hemihedral faces which in the tartrate were all turned the same way, were, in the paratartrate inclined sometimes to the right and sometimes to the left. In spite of the unexpected character of this result, I continued to follow up my idea. I carefully separated the crystals which were hemihedral to the right from those hemihedral to the left, and examined their solutions separately in the polarising apparatus. I then saw with no less surprise than pleasure that the crystals hemihedral to the right deviated the plane of polarisation to the right, and that those hemihedral to the left deviated it to the left; and when I took an equal weight of each of the two kinds of crystals, the mixed solution was indifferent towards the light in consequence of the neutralisation of the two equal and opposite individual deviations.Pasteur published its work in 1848 at the age of 26.[9–10] He made some idealized drawings of both forms of the racemate salt [11]Figure 3 Pasteur’s drawing of sodium ammonium tartrate crystalsBut these drawings make it look obvious. In reality the crystals look like thisFigure 4. Sodium ammonium tartrate. (left) l or (-) form. (right) d or (+) form.(bottom) racemate (+)(-) form. [12]Many articles on the web will mention that Pasteur was blessed with good luck: Sodium ammonium tartrate is one of the few tartrates that crystallize in two forms. In addition it only does that in a relatively small temperature range: above 26°C it forms a different crystal structure and if the temperature is too cold it will form small crystals that cluster together.I do not fully agree that it can be attributed to just luck.Other more experienced scientist failed to notice it. You must have a remarkable sense of detail to spot the difference. It is even more remarkable that you subsequently would use a microscope and start the tedious task to separate both crystal forms by hand.In a recent article published in Nature [13], Joseph Gal suggest that Pasteur’s artistic sensibilities and experience were instrumental in his discovery. At the age of 18 Pasteur he made a lithograph of one of his classmates. The final print of a lithograph is the mirror image of a carving in limestone, consequently Pasteur was very familiar with working with mirror images.Figure 5. Pasteur’s Lithograph (Images de la Vie et de L’œuvre de Pasteur (ed. Pasteur Vallery-Radot, L.) 59 (Flammarion, 1956).It’s probably one of the few chemical breakthrough experiments that is simple enough to repeat without too much effort:see e.g. [14].AFTERMATH.The importance of Pasteur findings is the existence of chiral [15] molecules. He discovered that the compound ‘racemic’ acid (‘bunch of grapes’) was in fact a mixture of natural tartaric acid and a different compound.Tartaric acid proper chemical name is 2,3-dihydroxybutanedioic acid. If we would draw the different forms using today's representation:Scheme 1: The different forms of tartaric acid using a skeletal drawing and Fischer projection.The natural tartaric acid is depicted on the left. Racemic acid is nothing more that an equimolar mixture of both enantiomers. The meso-compound (optical inactive) was not known at that time, but was discovered later by Pasteur himself In the same article he describes a better way to separate the enantiomers by adding an optical active salt.[16].But I skipped some steps with the above scheme: we must learn to walk before we can run.Pasteur’s only real experimental difference between both forms was that the natural compound rotated light to the right or (+) and his other compound rotated light to the left (-)In order to differentiate both forms chemists started to use a small d (from ‘dexter’, right) and a small l (from ‘laevo’, left) so natural tartaric acid would be called d-tartaric acid or (+)-tartaric acid (or a combination of the two: d-(+)-tartaric acid.)Unfortunately you can’t know the exact configuration from this simple optical property. In addition you should realize that at the time of Pasteur the theory of chemistry was still in development. After all the tetrahedral structure for carbon is only proposed in 1874. (Independently by the Dutchman Van't Hoff and the Frenchman Le Bel [17].) But with Pasteur stereochemistry started as one of the most important topics in organic chemistry.Since d/l nomenclature was useless, Fisher proposed to use a relative nomenclature. He took glyceraldehyde and called d-(+)-glyceraldehyde D-glyceraldehyde. [18]Scheme 2: Glyceraldehyde; the simplest ‘sugar’ used as starting point of D/L nomenclature by Fisher.Fisher arbitrarily put the chiral OH of D-glyceraldehyde at the right of his Fischer projection. He had 50% change that this would be correct.Based on glyceraldehyde as starting point you could deduce the configuration of other molecules. For instance by oxidation you can make glyceric acid. (But obviously if Fisher was wrong with his arbitrary configuration it would be incorrect in D-glyceric acid as well)Scheme 3: formation of D-glyceric acid (2,3-dihydroxypropanoic acid) from D-glyceraldehyde.Absolute proof of configuration was only established in 1951 by the team of the Dutch chemist J.M.Bijvoet [19] using X-ray’s and the resonant scattering effect. I do not think it is a coincidence they decided to use a tartrate salt sodium rubidium (+)-tartrate tetrahydrateThe result is that Emil Fisher's convention, which assigned the configuration of FIG. 2 to the dextrorotatory acid appears to answer the reality.In 1949 the German Jürg Waser actually came to a different conclusion [20]This is just the opposite configuration from the one assigned by E. Fischer on a postulatory basis.But luckily Bijvoet was correct [21], otherwise every chemical article before the 1950’s would be very confusing.The relative D/L nomenclature is still popular in sugar and amino acid chemistry. But in other subjects it has been replaced by the absolute R/S R(rectus) S (sinister ) nomenclature as proposes by Cahn, Ingold, and Prelog. (Absolute Configuration: R-S Sequence Rules)NOTES AND REFERENCES[1] Herschel, J. F. W. (1822). On the rotation impressed by plates of rock crystal on the planes of polarization of the rays of light, as connected with certain peculiarities in its crystallization. Trans. Camb. Phil. Soc. Vol 1, 43-52. Link[2] Biot, J. B. (1815). Phénomène de polarisation successive, observés dans des fluides homogènes, Bulletin des Sciences, par la Société Philomatique de Paris, 190-192. Link[3] We currently know that the SiO[math]_2[/math] molecules can form a left or right turning helix during crystallization.)Helix formation in Quartz (© Amir Akhaven)[4] Berzelius J.J. (1830). Om sammansättningen af vinsyra och drufsyra (John’s säure aus den Voghesen), om blyoxidens atomvigt, samt allmänna anmärkningar om sådana kroppar som hafva lika sammansättning, men skiljaktiga egenskaper. Kungliga Vetenskapsacademiens Handlingar, 49,‎ 49-80 linkTranslated to French: Berzelius J.J. (1831). Composition de l’acide tartrique et de l’acide racémique (traubensäure); poids atomique de l’oxide de plomb, et remarques générales sur les corps qui ont la même composition, et possèdent des propriétés différentes, Annales de Chimie et de Physique, 46,‎ 113-147 link (see page 131 for “paratartrates”)[5] Biot J. B.(1835). Mémoire sur la polarization circulaire et sur ses applications à la chimie organique, Mémoires de l'Académie des sciences de l'Institut, 2nd series, 39–175. Link[6]De la Provostaye H. (1841) Recherche Cristallographiques – acides tartrique et paratartrique, tartrates et paratartrates, Ann. Chim. Phys. 3 129 link[7] Biot J. B.(1844) Communication d’une note de M. Mitscherlich, Comptes Rendus XIX, 719 Link[8] Pasteur’s lecture delivered to the Société Chimique of Paris (translation from Researches on the Molecular Asymmetry of Natural Organic Products , Alembic Club Reprints, No. 14) Link[9] Pasteur L. (1848). Mémoire sur la relation qui peut exister entre la forme cristalline et la composition chimique, et sur la cause de la polarisation rotatoire" Comptes rendus de l'Académie des sciences (Paris), 26 : 535–538. link[10]Pasteur L. (1848). Sur les relations qui peuvent exister entre la forme cristalline, la composition chimique et le sens de la polarisation rotatoire", Annales de Chimie et de Physique, 3rd series, vol. 24, no. 6, pages 442–459. link[11] Pasteur L. (1850) Recherches sur les propriétés spécifique des deux acide qui composent l’acide racémique, Ann. Chim. Phys., 28 (3), 56–99. link and (Fig 1 and 4 on this page)[12] Yoshito Tobe (2003) The reexamination of Pasteur’s experiment in Japan Mendeleev Commun. 13, 93-94[13] Gal J. (2017) Pasteur and the art of chirality Nature Chemistry 9, 604–605[14] Kauffman George B. Myers Robin D (1975).The resolution of racemic acid: A classic stereochemical experiment for the undergraduate laboratory J. Chem. Educ. 52 (12), 777 link[15] Although he did not use that term: chirality was introduced by Lord Kelvin in 1894 and Mislow was the first to use the term in the context of chemistry in 1962)I call any geometrical figure, or group of points, 'chiral', and say that it has chirality if its image in a plane mirror, ideally realized, cannot be brought to coincide with itself (Lord Kelvin . "The Molecular Tactics of a Crystal". Clarendon Press. 1894)[16] Pasteur L. (1853). Transformation des acides tartriques en acide racémique ; — découverte de l’acide tartrique inactif ; — nouvelle méthode de séparation de l’acide l’acémique en acides tartriques droit et gauche, Comptes Rendus vol. 27, 162 link[17a] Le Bel J.A. (1874).Sur les relations qui existent entre les formules atomiques des corps organique et le pouvoir de leurs dissolutions Bull. Soc. Chim. Fr. 22: 337–347[17b]. Van't Hoff J.H.(1874) Arch. Neerl. Sci. Exact. Nat. 9: 445–454[18] I simplified this slightly: Fisher actually used a small d and l in his original publications, which was very confusing, so Rosanoff criticized Fisher’s nomenclature and proposed the Greek Letters δ and λ , later they used a capital D and L.see e.g. Fischer E. (1891) Ber. dtsch, chem. Gesellschaft 24, 2683-2687Rosanoff M.A. (1906) On Fisher classification of stereo-isomers J. Am. Chem. Soc. 28, 114-121 Link[19] M. Bijvoet, A. F. Peerdeman and A. J. van Bommel A.J. (1951). Determination of the Absolute Configuration of Optically Active Compounds by Means of X-Rays Nature 168, 271-272 doi:10.1038/168271a0[20] Waser Jürg(1949), The Absolute Configuration of d‐Tartaric Acid J. Chem. Phys. 17, 498 -499 link[21] Lutz Martin and Schreurs Antoine M. M. (2008). Was Bijvoet right? Sodium rubidium (+)-tartrate tetrahydrate revisited Acta Cryst. 64, 296–299 Reprint