hydrogenation over metals collection

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obituary
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08-13-01 17:20
No 204279

hydrogenation over metals

Here's a huge collection of material on the hydrogenation over metals:
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"Reactions of Hydrogen with Organic Compounds over Copper-Chromium Oxide and Nickel Catalysts"
by Homer Adkins (1937)

" The hydroxyl group in primary and secondary alcohols and phenols is so resistant to hydrogenolysis that the reaction has not been observed to occur over nickel or copper-chromium oxide at tempatures below 250, except when R contaions a phenyl, furyl. pyrryl, hydroxyl, carbonyl or carbalkoxyl group."

"For example, benzyl alcohol may be converted almost quantitively to
toluene over nickel at 100 to 125:"

"TABLE 27-Hydrogenation of carbon to oxygen bonds in aryl carbinols
(Carbinol to methylene)
[I'm going to have to change the format of the table so that i can post it, by the way no pressure was indicated...]

Benzyl alcohol-@ 125 C...10 min...2 gms Ni on keilsghur...(0.23 mol)
... converted to 88% toluene

Diphenylcarbinol-@ 200 C...3 hours...2 gms Ni on keilsghur...(0.17 mol)
...converted to 92% Diphenylmethane
"

===========================================================

"Organic Reactons"
editor in chief Roger Adams, 1953

"Table II
[alpha]-Substituted Benzyl Alcohols

Substance/Product/Yeild/Catalyst/Solvent/Temp/Pressure/Time
....
[ephedrine-HCl]/[-----HCl]/60-80%/Pd-BaSO4/CH3COOH+HClO4/80-90C
/1atm/10 minutes
"
===============================================================

"Catalytic Hydrogenation"
, by Robert L. Augustine, yr 1967

"The breaking of benzyl-oxygen of benzyl alcohols, ethers and esters
take place readily under mild hydrogenation conditions (44). [Bold
type ->] Ten grams of the benzyl compound is hydrogenolyzed over
1-1.5 g. of 5% palladium on charcoal in 75-100 mL of ethanol at room
tempature and atmospheric pressure. [Bold type end] The addition of
1-2 mL of concentrated hydrochloric, perchloric, or sulfuric acid
facilitates the reacton particularly for the cleavage of the more
diffuctly hydrogenolyzable compounds such as o-hydroxyl and
[alpha]-aminobenzylalcohols."
"[ephedrine] --(Pd/C @ 60C, H2SO4/H2O, 50-60psi)--> [methedrine]
95% [yeild]"

============================

"Catalytic Hydrogenation Over Platium Metals"
by Paul N. Rylander (1967)

"A solution of 82.6 grams l-ephedrine (XXVI) in 250 mL absolute ethanol
was reduced to XXVII [saturated ephedrine, or
C6H11-CHOH-CH(NHCH3)-CH3] without change in rotation over 1.6 gm
ruthenium dioxide at 1200 psig and 90 C in 40 minutes (Freifelder
and Stone, 1958). Hydrogenation over palladium black was accompanied
by reversal of rotation and, over platium oxide,
l-cyclohexylisopropylmethylamine was formed."

From a table from the same text:
Hydrogenation of benzyl alcohol- time in minutes for 50% completion,
unless otherwise stated in ()

SOLVENT/______5%-Pd+C/ 5%-Pt+C/ 5%-Rh+C/ 5%-Ru+C

++++++++++++++++++++++++++++++++++++++

WATER/________120 min/ 240 min(25%)/ 240 min(42%)/ 240 min(25%)

ACETIC ACID/__15 min/ 240 min (15%)/ 70min/ 240 min(4%)

METHANOL/_____160 min/ 240 min (0%)/ 40min/ 240min(0%)

ETHYLACETATE/_240 min(6%)/ 240 min(20%)/ 240 min(22%)/ 240 min(0%)

HEXANE/_______240 min(0%)/ 240 min(0%)/ 180 min/ 240 min(0%)

WATER + HClO4/28 min/ 240 min(30%)/ 130min/ 240min(0%)

====================================================

"Practical Catalytic Hydrogenations; Techniques and Aplications"
by Morris Frefelder, 1971.

" The use of Pd catalyst may be contradicted in the hydrogenolyses of
optically active, unsymetrical substituted benzyl alcohols, esters and
ethers if retention of configuration is desired. Pd causes inversion;
hydrogenation with Ni, Cu and Co catalysts favor retention of
configuration. These catalysts should be used in such instances if
reduction can be effected in their presence.

Removal of O-benzyl and related groups is enhanced by carrying out
reations in acidic media. When benzyl alcohols are reduced in acetic
acid or in acetic acid containing strong acid, deoxygenation is assumed
to proceed through the acetate. Since it has been shown that the rate
of displacement in reductions of compounds, ArCH2OR (where R = H,
CH3CO, CF3CO), is CF3CO > CH3CO > H, it might be advisible to add
trifluroacetic acid to hydrogenolysis when difficulty is encountered.

When deoxygenation of benzyl alochols is carried out in a nuetral
solvent containing mineral acid, reaction may proceed though an ester.
It may also go through a benzyl-type halide if hydrogen halide is
used to catalyize hydrogenolysis. It is also possible in mineral
acid-catalyzed hydrogenolyses of alcohols, ArCHOHCH2R, that dehydration
takes place, ArCH=CHR, followed by reduction of the double bond.

...

When O-debenzylation of a compound containing a basic nitrogen group
atom is to be carried out, it is advisable to use an equivalent of
acid to reduce the compound as an acid salt. ...

O-DEBENZYLATION AND RELATED REACTIONS

Arylmethanols

Benzyl alcohols, ArCH2OH, and related compounds generally are reduced
to hydrocarbons so readily in nuetral solution or in in acidic media
with palladium catalysts under mild conditions, that there does not
seem to be any reason to consider other catalysts for this purpose.

Nuclear substitution appears to have little effect on hydrogenolysis of
benzyl alcohols. ... The effect of an amino group on the activity of
the catalyst can be overcome easily by the addition of an equivalent
of of acid [2]. The presence of a bulky group adjacent to the -CH2OH
group may impede hydrogen uptake, but reduction in acetic acid or
acetic acid containing some strong acid should aid the deoxygenation."

=============================================================

"The Journal of the American Chemical Society", yr 1987, Vol 109,
pages 3459-3461

"Hetrogeneous Sonocatalysis with Nickel Powder

We have discovered that ultrasonic irradition of Ni powder increases
it's activity as a hydrogenation catalyst by >10^5. ...

The use of high-intensity ultrasound to initiate or enhance both
homogeneous and hetrogeneous chemical reactions has been under
intense investigation [1-7],...

Simple Ni powder is an extremely inactive catalyst for hydrogenation of
alkenes. Even after 2 X 10^4 min, no alkanes are deteacted with rapid
stirring under 1 atm of H2 at 273 K (i.e., <10 nM/min). In comparison
under the same conditions, if the nickel was first irradiated with
ultrasound [12], 1-nonene is hydrogenated at millimolar per min rates,
as shown on Figure 1. Ultrasonic pretreatment of ~1 h gives optimal
activity, which decreases with longer irradiation. The hydrogenation
activity is quite general and shows little dependance on the choice of
alkene... ; no reduction of ketones or aldehydes was observed.

Other methods of creating active Ni catalysts exsist [13]. The thermal
hydrogenation rates at 1 atm of H2 and 273 K with high surface area Ni
sponge (Raney Ni [13a], Aldrich Chemicals, grade W-2) are comparable
to those obtained eith ultrasoniclly activated Ni powder. Compared to
Raney Ni, however, our activaed Ni powder is more selective
(C-O double bonds are untouched), much easier to produce, and much
simpler to handle (nonpryophoric). Activation of Ni powders by H2 at
150 C and 10 atm will also generate reactive catalysts [13b], which
rapidily lose activity upon exposure to O2.

..."

[1] Adv, Organomet. Chem. 1986, 25, 73. (b) Modern Syth. Methods 1986,
4, 1. (c) Ultrasound: Its Chemical, Physical and Boilogical Effects
1987. (d) J Chem. Ed. 1986, 63, 427. (e) Ultrasonics 1985, 23, 157.

[2] J. Am. Chem. Soc. 1983, 105, 5781. (b) J. Am. Chem. Soc. 1983,
105, 6042. (c) High Energy Processes in Organomettalic Chemistry,
American Chemical Society 1987, p 191.

[3] High Energy Processes in Organomettalic Chemistry, American
Chemical Society 1987, pp 209-222. (b) Organometallics 1986, 5, 1257.
(c) Nachr. Chem. Tech. Lab. 1983, 31, 797. (d) J Org. Chem. 1982,
5030.

[4] Ultrsonics 1987, 25, 40. (b) Tetrahedron Lett. 1986, 27, 3149.
(c) J. Org. Chem. 1985, 50, 910, 5761. (d) J. Amer. Chem. Soc. 1980,
102, 7926.

[5] Angew. Chem., Intl. Ed. Engl. 1983, 22, 728. (b) J. Am. Chem. Soc.
1984, 106, 6856.

[6] Ultrasonics 1987, 25, 45. (b) J. Lab. Pract. 1984, 33, 13 and
references therein.

[7] Tetrahedron Lett. 1986, 27, 415. (b) J. Am. Oil Chem. Soc. 1983,
60, 1257. (c) Chim. Ind. (Milan 1968, 50, 314.

[12] All sonications were performed with a Heat Systems-Ultrasonics
W375 cell disruptor with a titanium immersion horn at acoustic
intensties of ~50 W/cm^2 at 20KHz, as described elesewher in
detail [2]. Irradiation in a low-intenstity ultrasonic cleaning bath
does give hydrogenation, but at greatly reduced rates. Hydrogenation
reactions were carried out at 273 K under 1 atm of H2. In a typical
reaction, 1 g of Ni powder (200 mesh, EM Science, Cherry Hill, NJ
08034) was added to a 10% solution of alkene in octane. ...

[13] Reagents for Organic Synthesis 1967, by Fieser, L. F., Vol. 1,
pp 723-731. (b) Thomas, C. L., Catalytic Porcesses and Proven
Catalysts 1970, pp 126-133. (c) Somorjai, G. A.; Chemistry in Two
Dimensions: Surfaces; 1981, pp 445-447 (d) J. Phys. Chem. 1983, 87,
915. (e) High Energy Process in Organicmetallic Chemistry,
... pp 223-245.

===========================

"Catalytic Hydrogenation Over Platium Metals"
by Paul N. Rylander (1967), page 321

"B. PLATINUM

Platinum catalyst have been used to achieve hydrogenolysis of a benzyl
function without saturation of the aromatic ring (Hartung and Simonoff
, 1953), but in many cases ring saturation may occur subsequently,
commitantly, or preferentially. ...

...

Benzyl oxygen functions may also be retained under approriate
conditions during ring saturation over platinum. Benzyl alcohol and
methyl-phenylcarbinol, compounds that readily undergo complete
hydrogenolysis over pallidium, were converted to the corresponding
saturated carbinols in nearly quantitative yield by hydrogenation
over prereduced platinum oxide in the presence of a trace of acetic
acid. As the amount of acetic acid was increased, hydrogenolysis
increased until the saturated hydrocarbon was the main product
(Nishimura, 1959). ..."

==============================

"Hydrogenation in Solutions"
by D. V. Sokol'skii, yr 1964,

Page 8
"...S. A. Fkin showed that the alcohol used as the solvent is itself
capable of adsorbing, in the presence of platinum, up to 7 mL of
hydrogen per 30 mL of alcohol. ...

...

The catalytic activity of platinum is temporarily reduced in the
presense of certain substances, such as formaldehyde and formic acid.
The apparatus, solvents, and the compounds be hydrogenated should
therefore be thoroughly cleaned. The catalytic activity of platinum
depends on the solvents. The best are water, alcohols, ethyl ether
and water soluble acids. Less suitible are petroleum fractions,
aromatic hydrocarbons, higher alcohols, and acids.

...

... The activity of collidial hydrogenation catalysts has been
overestimated up to the present day, and it will be of interest,
therefore, to examine the results of the earlier work carried out
mainly by Paal and his co-workers [3, 4, 5]."

[3]- Chem. Ber., 37, 124. 1904; 38, 1398. 1905.

[4]- Chem. Ber., 41, 805, 2273, 1908; 38, 1406, 2414. 1905; 40,
2209, 1907.

[5]- Chem. Ber. 41, 2282, 1908.

page 108
"The Catalyst Electrode

When the surface of a metallic catalyst is saturated with hydrogen in
a given medium, a reversible hydrogen potential is established which
may be measured by means of a reference electrode (e.g. calomel).
The value of the reversible hydrogenation potential depends on the
medium in which the measurement is carried out, and mainly, on the pH
of the solvent.

The equilibrium potential can be calculated by means of the Nernst
equation:

E = 0.58 log [H3O(+)] - 0.29 log P sub.(H2)

If the hydrogen is removed from the surface by anodic polarization or
by oxygen, the potential will shift to more positive values, and after
the complete removal of hydrogen, the potential will change to ~0.35 V
on platinum. Further anodic polarization results in a very rapid
increase in potential.

When the polarization is carried out at a very low current density, the
polarization curve is close to the equilibrium curve and the amount of
hydrogen absorbed on the surface can be readily esdtimated from the
position of the break on the curve. ... A. N. Frumkin and A. I.
Shlygin, ... called the curves obtained 'chronopotentiometric curves'.
The direct and reverse chronopotentiometric curves may be used to
calculate the amount of superficially adsorbed hydrogen and in certain
cases (when the capacity of a unit surface of the elctrode is known)
the true surface of the catayst electrode can also be calculated. ...

The adsorption of organic compounds on metallic surfaces also cause a
shift in potential, the magnitude and sign of the shift depending on
the nature of the adsorbed compounds. ...

...

When particles of a metallic catalyst powder are intensely agitaied in
solution they impart their potential to an auxliary wire electrode,
enabling the plotting of chronopotentiometric curves for the powder.
..."

page 110
"Electrical double layer and potential of gas electrodes

The contact of the catalyst electrode with the solution produces a
definite potential jump at the phase interface. ... Apart from metal
ions passing into solution and back, adsorption of other ions is also
possible. ...

In any solution of electrolyte, the concentrations of cation and anoins
are equal and the solution is electrically nuetral. If a metal
electrode is immersed in an electrolyte solution, the part of the
solution indirect contact with the electrode beomes enriched in
cations or anoins, forming the liquid plate of the so-called double
layer. ...

...

... it was demonstrated that, in a hydrogen-saturated platinum
electrode, hydrogen ions migrate into the solution and the elctrode
itself becomes negatively charged. ... This is the reason why alkali
is adsorbed from a solution of sodium sulfate rendering it acid
[1, 2]. ...

...

If a hydrogen-saturated electrode is anodically polarized, e.i., if
the concentration of electrons on it is diminished, the hydrogen atoms
absorbed on the surface will pass into solution, PtH -e --> Pt + H(+),
and this may easily detected from the change of pH of the solution."

page 130
"The system Pd - Ni

The systems Pd- Ni and Pt - Ni are extremely interesting because a
small amount of Pt and Pd deposited on the nickel catalyst increase
its catalytic activity many times. Studies on nickel-containing
systems are difficult, owing to their ready oxidation and solubilty
in acid media."

page 140
"The pallidium - platinum alloy possesses a higher cataytic activity
than is possessed separately by pallidium and platinum prepared under
identical conditions [49]. ... Thus, the mixed catalyst is 50 times
more active than platinum and apporaimately twice as active as pure
pallidium."

[1]- J. anorg. Chem., 158, 84. 1926.

[2]- Ber. Dtsch. chem. Ges., 60, 1816. 1927.

[49]- Ibid.,4 60. 1951.

page 388
"In an overwhelming majority of cases, the hydrogenation rate in
solution is directly porportional to a hydrogean presure, up to a
certain limit. ... it was shown that in the hydrogenation over Raney
Nickel the reaction order with respect to hydrogen changes from unity
to zero at pressures of 10 to 20 atm. In isolated cases, especially
at high tempatures (~200 [degrees]), the reaction rate continues to
increase also at pressures above 50 atm."

From appendix:
HYDROGEN-ETHANOL
===================
Tempature C / Solublity, cm^3 per 1 cm^3 of alcohol
1 / 0.06916
5 / 0.06847
11.4 / 0.06765
23.7 / 0.06633

Solublity @ 25 C, cm^3 per 1 cm^3 of solvent
Pressure, atm / hydrogen-water / hydrogen-methanol
10 / 0.19 / 0.9
20 / 0.38 / 1.8
30 / 0.57 / 2.9
40 / 0.76 / 3.4

Solublity, cm^3 per 1 cm^3 of water
Temp, C / hydrogen-water / oxygen-water
0 / 0.0214 / 0.0496
5 / 0.0203 / 0.0439
10 / 0.0193 / 0.0390
15 / 0.0185 / 0.0350
20 / 0.0178 / 0.0317

25 / 0.0171 / 0.0290
30 / 0.0163 / 0.0268
40 / 0.0153 / 0.0233
50 / 0.0141 / 0.0207
60 / 0.0129 / 0.0189
70 / ------ / 0.0178
80 / 0.0085 / 0.0172