8. Chemistry of the Main Group Elements 8b small.pdf · Chemistry of the Main Group Elements ... 14 8. Chemistry of the Main Group Elements ... in an inorganic chemistry laboratory:

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8. Chemistry of the Main Group Elements

The Group 14 Elements

http://www.chemsoc.org/viselements/pages/pertable_fla.htm

Carbon (C)

non-metal


The Group 14 Elements - Carbon

Isotopes of Carbon:

Nuclide Atomic Mass Nat. Abd. Nucl. Spin12C 12.000 000 000* 98.90 0 13C 13.003 354 826 1.10 ½

unstablenuclides Atomic Mass Half life Decay Mode10C 10.016 86 19.3 s β+ 3.650 MeV11C 11.011 43 20.3 m β+ (EC) 1.98214C** 14.003 241 5730 y β− 0.156

*) by definition**) traces of this isotope occur naturally

NMR

radio-carbondating

2


Carbon - Fractionation of Isotopes

13C12C sample

13C12C std

−

13C12C std

x 1000δ13C =

positive δ13C value: sample has a greater proportion of the heavier isotope of carbon, 13C

negative δ13C value: depleted in the heavier isotope

values in 0/00 (per mil, ppt)

standard: carbon contained in calcite from fossils called belemnites from a particular limestone called the Pee Dee Formation (abbrev. as PDB).


Carbon – Radiocarbon Dating

14C nat. abd.: 10 −12% τ1/2 = 5730 yβ − 0.156 MeV

in the upper atmosphere: 147N + 10n -> 14

6C + 11H

14C + O2 -> 14CO + O

14CO + •OH -> 14CO2 + H•

Equilibrium of 14CO2 formation and radioactive decay

-> 14CO2/12CO2 global scale steady-state equilibrium hydrosphere & biosphere, photosynthesis etc.

-> 14C/12C atomic ratio = 10 −12

Willard Libby(Nobel 1960)

3


Carbon – Radiocarbon Dating

…once the exchange ceases (e.g. death of biomaterials), the radioactive clock starts running and the age of an object can be determined from the decreasing 14C/12C ratio.

Radiocarbon age limit : 58,000 and 62,000 years (radioactivity of the residual 14C in a sample is too low to be distinguished from the background radiation)

K-Ar and U decay series are used in dating older objects


Carbon - Modifications

+ 1.899 kJ

1500 oC

1500 –1800 oC,53000-100000 bar

4


Carbon - 3rd Modification in Nature (1985) 318, 162


Carbon - 3rd Modification:

US Pavilion @ 1967 Montreal World's Fair by Buckminster Fuller

5


Carbon - 3rd Modification in Nature (1985) 318, 162

Richard Smalley & Robert F. Curl (left)(died Oct. 28, 2005) Rice University

Sir Harold W. Kroto (University of Sussex, now Florida State)

Nature (1990) 347, 354



Studying the conditions under which carbon nucleates(in a He-atmosphere)

graphite electr.15V – 150 Amps~ 100 Torr Hegenerates sootextract soot w/e.g. tolueneseparate onalumina gel column

http://engineering.dartmouth.edu/other/nanomaterials/reu2001/Pasquini.htm

Krätschmer Apparatus

6



C60 C70


Carbon - Modifications

C60

C60 End View

C20

C70

carbon nanotube

7



C540

C20


Carbon - Compounds CH4, CH3OH, HCOH, HCOOH, CO2

-4 -2 0 +2 +4

8


Carbon - Compounds

Al4C3 + 12H2O -> 4Al(OH)3 + 3CH4

CaC2 + 2H2O -> Ca(OH)2 + HC≡CH

d(C≡C) = 119 – 124 pm in MC2for M = group 2 metal

d(C-C) = 128 – 130 pm for M = lanthanides


Carbon - Compounds

CaC2 + 2H2O -> Ca(OH)2 + HC≡CH

carbide lampacetylene burner

9


Carbon - Compounds

…a terminalMo-carbidocomplex

C.C. CumminsChemCommun1997, 1994




Nitrogen (N)

10



Nitrogen (N)N2 N≡N and N2

2− in SrN2 122.4 pm

N3− [N≡N—N]− [N=N=N]− [N—N≡N]−

N5+

N≡N—

N—N≡N

+ AsF6−

[N2F+](AsF6−) + HN3

real crazy

stuff

How about N5+N3

− (N8) and WHY???High-Energy-Density Materials…

Propellants, Explosives etc.

NaN3 vs. AgN3Pb(N3)2

N3− in TM nitridocomplexes



N5+

N≡N—

N—N≡N

+ Sb2F11−

K. O. Kristie JACS (2001) 123, 6308

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Nitrogen – Hydrogen Compounds

NH3: from the elements N2 & H2elegant prep.: Nitrogenasepoor attempt: Haber-Bosch

fertilizers & explosivessynthetic fibers, e.g.,nylon, polyurethanesorganic & inorg. synth.non-aq. ionizing solvent

N2H4: N2H4 + O2 -> N2 + 2H2O

ΔH0= −622 kJ/mol


Nitrogen –Hydrogen Compounds

N2H4: N2H4 + O2 -> N2 + 2H2O

ΔH0= −622 kJ/mol

A clear, highly toxic & carcinogenic, NH-compound with a fishy smell

Rocket Fuel: 50% N2H4/50% UDMA(UDMA: unsymmetrical Me2NNH2)

Hydrazine in a 70% solution is used to power the EPU (Emergency Power Unit) on the F-16 fighter plane.

F-16’s EPU

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Nitrogen –Hydrogen Compounds

N2H4: N2H4 + O2 -> N2 + 2H2O

ΔH0= −622 kJ/mol

Reducing agent e.g. in plutoniumextraction from reactor waste


Nitrogen Oxides (NOx) & Oxoanions

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N2O: mild dental anestheticenvironmentally acceptablesubstitute for FClC’sNO: TM ligand very reactive, toxic gas, and yet,…biologically important: NO Synthases: nNOS, iNOS, andendothelial NOS (lumen bloodvessels)

NH2

C NH2

NH(CH2)3

CHNH2

COOH

NOS

2NADPH

2O2

NH2

C O

NH

(CH2)3

CHNH2

COOH

+ NO

2NADP

2H2O

arginine citrulline



NO: …biologically important

Blood Flow: NO relaxes smoothmuscles in blood vessels.

Birth: NO inhibits contractilityof smooth muscle wall of uterus.

Kidney function: NO increasesblood flow in kidney cells thus,increasing rate of filtration.

Inflammation: No inhibits in-flammation in blood vessels.

Secretion: NO affects secretionfrom several endocrine glands.

and, and, and…

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NO2: in equilibrium w/ N2O4

can be formed in atmosphere(e.g. lightning on N2 & O2)forms via combustion of fossilfuels -> “acid rain”

3NO2 + H2O -> 2HNO3 + NO

HNO3: for NH4NO3 mass prod.

2NH4NO3 -> 2N2 + O2 + 4H2O+ ΔE

fertilizer & explosives

Fritz Haber, Nobel Prize 1918for “potatoes from air”

NH3 + O2 + cat -> NO + air + H2O -> HNO3 -> NH4NO3 (explosives)


Nitrogen Oxides & Oxoanions

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Nitrogen Oxides, Oxoanions & Acids


Nitrogen – Rich Redox Chemistry

moststable

leaststable

good playground to practice formaloxidation states…

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…a little bit of Phosphorous Chemistry: stable polymers

red phosphorus

black phosphorus

no allotrope,but mixture:

violetphosphorus

Hittorf’s P


…a little bit of Phosphorous Chemistry: stable polymers

black P (~ graphite)

violet P

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…by far the most exciting allotrope: monomeric P4

White Phosphorus P4(g) W P2(g)

very toxic & reactive with air (O2) α-form (cubic) condensation from gas phase, slowly transformsto β-P4 (above −76.9oC)

@ 1070K

221

ppm


…a little bit of Phosphorous Chemistry:

Very toxic & reactive with air White Phosphorus (P4)α-form (cubic) condensation from gas phase, slowly transformsto β-P4 (above −76.9oC)

Phos

phor

esce

nce

!

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Oxygen (O)


Dioxygen 3Σg

σs

σp

πp

σ∗s

σ∗p

π∗p

2s

2p , p , px y z

oxygen A'satomic orbitals

oxygen B'satomic orbitals

dioxygenmolecular orbitals

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Dioxygen

πp πp πp πp

σp σp σp σp

π∗p π∗

p π∗p π∗

p

32O 2

2O •− O22− 1

2 O ( )1Δ 12O ( )1Σ

reduced formsground state excited-state forms

Bond Order

Bond Length [pm]

VibrationalFrequency [cm ]-1

2 1.5 1 2

+ 90 kJ/mol + 150 kJ/mol

121 ~ 128 ~ 149

1560 1150 - 1100 850 - 870


Dioxygen - Species

formed from rxn of O3 w/ dry alkali metal hydroxides, decomp.

134ozonideO3−

bond angle 116.80, strong oxidizer, absorbs <320nm (UV)

127.8ozoneO3

forms ionic compounds w/ alkali metals, strong oxidizer

149peroxideO22−

moderate oxidiz. agent, stable compounds incl. KO2, RbO2, CsO2

128superoxideO2−

coordinates to transition metals singlet O2 important photochem. & oxidizing reagent

120.7dioxygenO2

BO = 2.5112.3dioxygenylO2+

Notesd(O—O)pm

NameSpecies

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8. Chemistry of the Main Group Elements(a little excursion)

Dioxygen Chemistry

4Fe2+ + O2 + 2H2O + 8OH- -> 4Fe(OH)3 -> 2Fe2O3 + 6H2O

…in your garage:

…in an inorganic chemistry laboratory:

M

M

M

M

MM

M

M

MOO

O

O

O

O

O

OO

O

O

OO

O

M

M

M

MM

O O

M

M

M

M

O

O

Dioxygen


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Dioxygen Chemistry

4Fe2+ + O2 + 2H2O + 8OH- -> 4Fe(OH)3 -> 2Fe2O3 + 6H2O

…in your garage:

…in an inorganic chemistry laboratory:

M

M

M

M

MM

M

M

MOO

O

O

O

O

O

OO

O

O

OO

O

M

M

M

MM

O O

M

M

M

M

O

O

…nothing compared to:



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Dioxygen Chemistry

…in hemo & myoglobin:

The imidazole ring of the distal His E7 (pK = 5.5 ) acts a a proton trap, thereby protecting the iron ion from H+.

Linearly coordinatedCO binds ~ 25,000 more tightly to Fethan dioxygen does.

A bent Fe—CO geometry weakensthe ligand interaction significantly. CO binds“only” 200x stronger.

The dioxygen ligandbinds to the iron-hemewith an Fe-O-O angleof ~ 115 – 159o.

also…think aboutmaternal &fetal blood and fetal O2support!?


…in hemoglobin: O2 binds cooperatively, is pH dependent, &, &…!

MeOH poisining…what happens &how is it treated ?


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Ozone Chemistry

…and depletion of the (protecting!) ozone layer:

in the upper atmosphere:

O2 + hv(λ<320nm) -> 2O

O2 + O -> O3 -- forms indispensable protective shield

howeverNO2 + O3 -> NO3 + O2

NO3 -> NO + O2NO + O3 -> NO2 + O2

2O3 -> 3O2 …very simple, very bad!

♦ add. note: O3 stronger oxidizer than O2, only exceeded by F2


(back to the roots)


rhombic sulfur (S)

[Sα W Sβ] W [Sλ W Sπ W Sμ] W [S8 W S7 W S6 W S5 W S4 W S3 W S2 W S]

rhombic monoclinicsolid sulfur

liquid sulfur

dark redrhombic monoclinic

gaseous sulfur

95.60C

444.60Cbpt.

119.60Cmpt.

444.6 to 22000C

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[Sα W Sβ] W [Sλ W Sπ W Sμ] W [S8 W S7 W S6 W S5 W S4 W S3 W S2 W S]

rhombic monoclinicsolid sulfur

liquid sulfur

dark redrhombic monoclinic

gaseous sulfur

95.60C

444.60Cbpt.

119.60Cmpt.

444.6 to 22000C


[S42− W 2S2

−] [S62− W 2S3

−]yellow-green

blue

[S82− W 2S4

−]red

Sulfur-anions

Deep blue lazurite (lapis lazuli) [(Na3Ca)8(Al(SiO4))3(S)]

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Sulfur: very rich S-O and H2SnOm Chemistry



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S + O2 -> SO2 combustion of sulfur

MxSy + O2 -> ySO2 + MxOy roasting of sulfide ore

SO2 + O2 -> SO3 multi-step V2O5 cat.

SO3 + H2O -> H2SO4 sulfuric acid

SO3 + H2SO4 -> H2S2O7 disulfuric acid (oleum)

also known H2SO2, H2SO3, H2SO5H2S2O2, H2S2O3, H2S2O4, H2S2O5, H2S2O6H2S2O7, H2S2O8…

great exerci

se to

check fo

r stru

ctures

& form

al ox.-st

ates

big-timeacid

anhy-dride

no trueacid

anhy-dride




Fluorine (F)

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Helium (He)



Description :A colorless, odorless gas that is totally unreactive. It is extracted from natural gas wells, some of which contain gas that is 7% helium. It is used in deep sea diving for balloons and, as liquid helium , for low temperature research. The Earth’s atmosphere contains 5 parts per million by volume, totaling 400 million tons, but it is not worth extracting it from this source at present.

Discovered : by Sir William Ramsay in London, and independently by P.T. Cleve and N.A. Langlet in Uppsala, Sweden in 1895

Discovered : by Sir William Ramsay and M.W. Travers in 1898 (London, UK)

Origin : Greek ‘neos’ (new)

Description :A colorless, odorless gas that comprises 18 parts per million of air. Neon will not react with any other substance. It is produced from liquid air for ornamental lighting (i.e. neon signs) because it glows red when an electrical discharge is passed through it.

Discovered : 1899 by Lord Rayleigh and Sir William Ramsay

Origin : Greek ‘argos’meaning inactive.

Description :The third most abundant gas, making up one percent of the atmos-phere. The quantity has increased since the Earth was formed because radioactive potassium turns into argon as it decays. Argon is a colorless, odorless gas that is totally inert to other substances, and for this reason it is ideal in light bulbs.

Discovered : by Sir William Ramsay and M.W. Travers in 1898

Origin : Greek ‘kryptos’, meaning hidden

Description :A colorless, odorless gas that is inert to everything but fluorine gas. The isotope krypton 86 has a line in its atomic spectrum that is now the standard measure of length : 1 meter is defined as exactly 1,650,763.73 wavelengths of this line. Krypton is one of the rarest gases in the Earth’s atmosphere, accounting for only 1 part per million by volume.

Discovered : by Sir William Ramsay and M.W. Travers in 1898

Origin : Greek ‘xenos’, meaning strange.

Description :A colorless, odorless gas that makes up 0.086 parts per million of the atmosphere. About half a ton a year is produced from liquid air and used for research purposes.

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8. Chemistry of the Main Group Elements 8b small.pdf · Chemistry of the Main Group Elements ... 14 8. Chemistry of the Main Group Elements ... in an inorganic chemistry laboratory: