Chemistry 125: Lecture 21October 22, 2010

Berzelius, Gay-Lussac, & Davy (1805-1830)

Wöhler’s Isomerism (1828) Liebig’s Analysis (1831) Berzelius improved Dalton’s atomic weights as well as combustion analysis for organic

compounds. Together with Davy in London and Gay-Lussac in Paris, he discovered new

elements by electrolysis, which also led to the theory of dualism, wherein atoms were united

by electrostatic attraction. Wöhler’s report on the synthesis of urea reveals a persistent

naiveté about treating quantitative data. His discovery of isomerism made it clear that there

was more to chemical substances than which atoms they contained and in what ratios. The

progress of structural chemistry throughout the 19th Century depended heavily on C & H

analysis using Liebig’s profoundly simple “Kaliapparat”. Work by Wöhler and Liebig on

benzaldehyde inspired a general theory of organic chemistry focusing on so-called “radicals” -

collections of atoms that appeared to behave as elements and to persist unchanged through

organic reactions.For copyright

notice see final page of this file

BerzeliusJöns-Jakob

BERZELIUS(1779-1848)

Organic & Mineral

Analysis

Dualism(double decomposition)

Electrolysis

Notation forComposition

Teaching& Writing

Textbook(1808)

2000 compounds in 6 years!

Good Atomic Weightsfor 50 elements!

Berzelius’sTable ofatomic & molecular weights

(1831) Weights

Based on O = 100 or H2 = 1

O = 15.9994

[15.999]

0.998 (-1.0%)

14.162 (-1.0)

32.185 (0.4)

30.974 (1.3)

Bars denotedoubled atoms

Scaled to modern

discrepancy from modern

value

10-fold increase in accuracy from Dalton!

CombustionAnalysis

Berzelius Analysis

(1) Tube 1/2” diameter (Fig 1) charged with dried powder containing: ~0.5 g of organic substance to be analyzed,

3 g NaClO3 (Gay-Lussac’s O2 source), 50 g NaCl (to moderate reaction by dilution).

(2) Neck of tube heated and drawn out (Fig 2)

(4) Assembled (Fig 6) so that gases (O2, CO2) that exit drying tube will bubble into bell-jar containing Hg

with floating bulb (Fig 5) holding KOH (to absorb CO2) and closed with permeable glove leather (to keep out Hg).

Improved Method of Combustion Analysis

(3) Joined (Fig 4) to water-collecting bulb (Fig 3) and CaCl2 drying tube with rubber tubing

Berzelius Analysis

(6) To be certain the KOH absorbs all of the CO2 through the glove leather, wait 12 hours after the mercury stops rising in the bell jar before disassembling and weighing.

(5) Build fire in brick enclosure to heat tube slowly from near end to far. Tube wrapped with metal sheet to keep it from popping when it softens at red heat under the pressure necessary to bubble through Hg.

Improved Method of Combustion Analysis

O2

KOHCO2

Electricity

New York Public Library http://seeing.nypl.org/152t.html

N2O at theRoyal Institution

London, 1802

HumphryDavy

Pile 1799

VoltaBattery of Berzelius

1807-8Humphry Davy

Big Scienceat London’s

Royal Institution

Electrolysis

Cu Zn “couple”

1.1 v

301

v

26 v

110 v

165 v

12×12”

4×4”

6×6”

Davy (1808)

I acted upon aqueous solutions of potash and soda, saturated at common temperatures, by the highest electrical power I could command, and which was produced by a combination of Voltaic batteries belonging to the Royal Institution, containing 24 plates of copper and zinc of 12 inches square, 100 plates of 6 inches, and 150 of 4 inches square…

…though there was a high intensity of action, the water of the solutions alone was affected, and hydrogen and oxygen disengaged with the production of much heat and violent effervescence.

Davy (1808) The presence of water appearing thus to prevent any decomposition, I used potash in igneous fusion. By means of a stream of oxygen gas from a gasometer applied to the flame of a spirit lamp, which was thrown on a platina spoon containing potash, this alkali was kept for some minutes in a strong red heat, and in a state of perfect fluidity. The spoon was preserved in communication with the positive side of the battery of the power of 100 of 6 inches, highly charged; and the connection from the negative side was made by a platina wire. By this arrangement some brilliant phenomena were produced. The potash appeared a conductor in a high degree, and as long as the communication was preserved, a most intense light was exhibited at the negative wire, and a column of flame, which seemed to be owing to the development of combustible matter, arose from the point of contact.

Davy (1808)

A small piece of pure potash, which had been exposed for a few seconds to the atmosphere, so as to give conducting power to the surface, was placed upon an insulated disc of platina, connected with the negative side of the battery of the power of 250 of 6 and 4, in a state of intense activity; and a platina wire, communicating with the positive side, was brought in contact with the upper surface of the alkali.

…small globules having a high metallic lustre, and being precisely similar in visible characters to quick-silver, appeared, some of which burnt with explosion and bright flame, as soon as they were formed, and others remained, and were merely tarnished, and finally covered by a white film which formed on their surfaces.

Napoleon’s Response (via Gay-Lussac)

1807-8Humphry Davy

Big Scienceat London’s

Royal Institution

600 1 kg Cu plates600 3 kg Zn plates

2.6 tons of metal

~650 v

“...on his alluding to the taste produced by the contact of two metals, with that rapidity which characterised all his motions, and before the attendants could interpose any precaution, he thrust the extreme wires of the battery under his tongue, and received a shock which nearly deprived him of sensation. After recovering from its effects, he quitted the laboratory without making any remark, and was never afterwards heard to refer to the subject.” from: “The Life of Sir Humphry Davy, Bart.”

2,200 v

Li Be B

Na Mg Al

K Ca Ga

Rb Sr In

Cs Ba Te

Electricity supplied more than new elements...It also supplied the

organizing principle for

Dualism

ChemicalSymbolsof 1774(Sweden)

1774 Symbols

Mix with Caustic Soda

"Double Decomposition"

A B + C D A D + C B+ + + +- - - -

Explained by Electricity

Dualism

CuSO42 NaOH Na2 SO4 Cu (OH)2+ +

precipitate

“Electronegativity”

First use in English (according to O.E.D.)

1837 J. D. Dana Syst. Mineral. 82 When chemistry has so far advanced, that the relative electro-negativity, (if I may so call it,) or electro-positivity, of the several elements, is fully known,..we shall probably be able to construct a natural arrangement of minerals on chemical principles.

J. D. Dana1813-1895

son-in-lawof Benjamin

SillimanDana House

1849

Genealogy Top

Wöhler/Liebig

to J.J. Berzelius Heidelberg, 17 July, 1823

“Having developed the greatest respect for you through studying your writings, I have always thought it would be my greatest good fortune to be able to practice this science under the direction of such a man, which has always been my fondest desire.

Although I earlier had planned to become a physician…”

With the greatest respect

F. Wöhler from Frankfurt am Main

Friedrich Wöhler(1800-1882)

Letter to Berzelius (1837)

“To see this old friend [Palmstedt] again, especiallyhere [in Göttingen], was a real delight. He was just the same old guy, with the sole exception that he no longerwears the littletoupee swept up over hisforehead ashe used to do.”

1828

Urea&

Isomerism(problems for Monday, Oct. 25 - see web readings)

Wöhler to Berzelius (1828)

"Perhaps you still remember the experiment I carried out in that fortunate time when I was working with you, in which I found that whenever one tries to react cyanic acid with ammonia, a crystalline substance appears which is inert, behaving neither like cyanate nor like ammonia."

"Ammonium Cyanate"from Double Decomposition

NH4 Cl + Ag OCN NH4 OCN + Ag Cl+ + + +- - - -

NH3

NaOH

OCNH

H+ Pb++

Pb(OCN)2

HNO3

Brilliant Crystal Flakes(Just like those from Urea + HNO3)

Not like an ammonium

salt!

Not like a cyanate salt!

Might Ammonium Cyanate Be Urea?

Wöhler to Berzelius: "I recently performed a small experiment, appropriate to the limited time I have available, which I quickly completed and which, thank God, did not require a single analysis."

Berzelius to Wöhler: "It is a unique situation that the salt nature so entirely disappears when the acid and ammonia combine, one that will certainly be most enlightening for future theory…"

Prout’s ExperimentProut N2 by gas volume:

Prout’s theory was better than Berzelius’s experiments!

Experimental Candor?Prout did dry-lab by making an approximate analysis and reporting results “corrected” by his theory!

better than Berzelius’s Theorytruncated instead of

rounding up

Urea had already been AnalyzedApprox.

AtomRatios

1121

NCHO

Total

Dr. Prout(1817)

46.65019.9756.67026.650

99.875

46.7820.19//6.5926.24

99.80

Recalc.(from

Berzelius)

46.78120.19806.59526.425

100.000

Discrepancies <2% identical

Dyslectic Error(& he didn't notice!)

Prout’s Atomic Weight Theory: H = 1 ("protyle" ) C = 6 ; O = 8 ; N = 14

?99.945

(added wrong)

46.6520.00

6.7126.64

100.00

Modern

Moral: Don’t dry-lab! (like Lavoisier)Just Lucky?

Paragon of accuracy and honesty

NH4OCN(calculated by Wöhler

from Berzelius atomic weights)

"6.3 cubic inches"V, T, P within 0.02%?

?

Ammonium Cyanate to Urea

H N H

H

H

N C O

H N

H

H

N C OH

H

N HH

N C OH

H

N HH

N C OH

n*

n *

n*

poor overlap probably

intermolecular

Can ammonium cyanate exist?

ResonanceStructures!

NH2

H2NC

OHH

make & break

attack *

C=O very stable (lore)

Dunitz, Harris, et al. (1998)

Wöhler on Isomerism (1828) "I refrain from all the considerations which so naturally suggest themselves from this fact, especially in respect to the composition ratios of organic substances and in respect to similar elemental and quantitative compositions among compounds with very different properties, as may be supposed, among others, of fulminic acid and cyanic acid and of a liquid hydrocarbon and the olefiant gas, and it must be left to further investigations of many similar cases to decide what general laws can be derived therefrom."

On the Composition of Tartaric Acid and Racemic Acid (John's Acid from the Vosges Mountains), on the Atomic

Weight of Lead Oxide, together with General Remarks on those Substances with have the Same Composition but

Different Properties. by J. J. Berzelius (1830)

"I have thought it necessary to choose between the words : homosynthetic and isomeric substances. The former is built from homos, equivalent, and synthetos, put together; the latter from isomeres has the same meaning, although it only properly says put together from the same pieces. The latter has the advantage with respect to brevity and euphony, and thus I have decided tochoose it." "By isomeric substances I understand those which possess the same chemical composition and the same atomic [molecular] weight, but different properties."

X-Ray showed thatthese crystals are

Calcium Tartrate • 4 H2O

There is more to chemistry than Berzelius’s analytical

COMPOSITION!Now we know the importance of

atomic arrangement, or STRUCTURE:

CONSTITUTION

CONFIGURATION

CONFORMATIONbut we need to be patient.

HNCOIsomer

EnergiesW.D. Allen et al., J. Chem. Phys.,

120, 11586-11599 (2004)

OCN -3.1

OC N +56.3

OCN -27.8

Cyanic Acid (Wöhler)

Fulminic Acid (Liebig)

"we have pushed ab initio quantum chemistry to its current limits for the species NCO, HNCO, HOCN, HCNO, and HONO, all in pursuit of subchemical accuracy (approximately 0.1-0.2 kcal/mole)"

(Latin fulmen = lightning)

ONC +40.9+ _

(same NCO anion interconvert easily)

(same CNO anion)

with Gay-Lussac, who noticed the analysis was like

Wöhler's ofSilver Cyanate

Liebig 1836JustusLiebig(1803-1873)

1824 in Paris working on

Silver Fulminate with Gay-Lussac,

SCL

SCL Library

Liebig Analysis (1831)

H2OCollector

Combustion

CO2 Collectortilted

(1837)

cushioned

Kaliapparat

in

Backwards!Big

inoutout

1852

Lab

Liebig’s Laboratory in Giessen

Stammbaum

Some Liebig Scientific Descendants

Red = Nobel Prizeyou

Lab Workers?

A master and glittering teacher of chemistry

the triumphant discovererof aniline and aniline dyes

1832

Radical Theory

Correspondence of Liebig & Wöhler Winter 1825 - Wöhler and Liebig first meet in Frankfurt.

October 1830 - They first write using familiar “Du”.

16 May 1832 - Wöhler: I long to do some more significantwork. Shouldn't we try to shed some light on the confusion about the oil of bitter almonds?But where to get material?

15 June 1832 - Liebig: My poor, dear Wöhler, how emptyis every comfort against such a loss…When I think how content and happy you were during your move, what attachment and love you had for one another…The good wife, so young, so full of life, and so irreplaceable for her parents and for you…

Correspondence of Liebig & Wöhler Come to us, dear Wöhler, although we may not be able to give you comfort, we will perhaps be able to help you bear your grief. Staying in Cassel at this time would only be detrimental to your health. We need to be busy with something, I have just been able to get some amygdalin from Paris, and I am ordering 25 pounds of bitter almonds. You must not travel, you must busy yourself, but not in Cassel. I haven't had the courage to tell my wife yet. I can only tell her bit by bit because I know how much it will affect her. Come to us, I expect you at the end of this week.

End of Lecture 21

October 22, 2010

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