A practical experiment

1. The Synthesis and Analysis Of
Hydrazine
By Kenn D. Thomas
Partner: Kaleeb Watson
Date; 31.01.05

2. 1
The Synthesis and Analysis of Hydrazine The presence of trace metals such as copper may catalyze this
reaction. This is prevented by addition of a chelating agent.
Kenn D. Thomas and Kaleeb Watson
The Olin-Raschig process is a modification of the Raschig
synthesis in which liquid chlorine is continuously absorbed into dilute
The University of the West Indies, Chemistry Department, Mona,
NaOH forming sodium hypochlorite, which is made to react with excess
Jamaica, West Indies.
ammonia, followed by large excess anhydrous ammonia under
○
pressure, which raises the temperature to 130 C preventing the
decomposition of hydrazine by chloramines
ABSTRACT
The Ketazine process is another process for the manufacture of
hydrazines.In this process, hydrazine derivatives. Ammonia is first
Hydrazine is a compound used historically as a propellant but is
oxidized by chlorine or chloramines in the presence of aliphatic
currently used in the pharmaceutical, agricultural and industrial sectors.
ketones
It is produced commercially using the Raschig process. This
to produce hydrazones and isohydrazones. These are then converted
experiment used the Raschig synthesis on a laboratory scale, the
to ketazines with addition of excess ketone. The ketazines (the
hydrazine formed was isolated as the sulfate, then tested qualitatively
intermediate hydrazine derivatives) may be hydrolyzed to hydrazine
using known reactions of hydrazine, followed by volumetric analysis
after all the oxidizing reactants, such as chlorine, hypochlorite and
using the Andrews titration. The maximum theoretical yield was
chloramines are consumed. Ketazines do not readily oxidize thus the
136.663g; however the actual yield was 3.77g or 2.75 %.The
yield is higher in these processes.
recrystallized precipitate showed positive results when subjected to
There are many other methods of hydrazine production, most
qualitative tests for hydrazine. Subsequent Titrimetric analyses show
of which are based on the oxidation of ammonia by different oxidizing
that this precipitate was composed of 25-36 % hydrazine by mass. The
agents. These methods are exemplified by the oxidation of ammonia
Raschig synthesis is economical on the large scale; however it is
with hydrogen peroxide in the presence of methyl ethyl ketone,
inefficient in the laboratory scale synthesis of hydrazine.
acetamide and disodium hydrogen phosphate at 50°C:
INTR0DUCTION
C 2H 5
CH3CONH2
Hydrazine was first isolated as sulfates by Curtius in 1887.Its
2NH3 + H2O2 + 2CH3COC2H5 C 2H 5
organic derivatives were prepared earlier in 1875 by Fischer then Na2HPO4
Raschig prepared Hydrazine by hypochlorite oxidation of ammonia in 50°C
+ 4 H 2O
1
1906 . H 3C N
Hydrazine was used originally as rocket propellant; in World War
N CH3
II it was used as fuel for rocket powered planes. The use of Hydrazine
The synthesis of hydrazine can also be achieved by the oxidation of
as fuel is at present quite limited, NASA uses hydrazine as fuel for
urea NH2CONH2 in place of ammonia.
2
orbiting satellites , but its use as a primary rocket fuel is limited by
Hydrazine can undergo many reactions due to its basicity (from the
3
economic constraints as well as safety concerns . Hydrazine currently
lone pair of electrons on each nitrogen atom).It undergoes self
finds uses in pharmaceuticals, in water treatments (it binds to
ionization, it can take part in many redox reactions and it can form
dissolved iron), as blowing agents; in insect control; in fuel cells; in
complexes with several metals (table 1.0).
polymers. The derivatives of hydrazine are used in agricultural
Hydrazine can be analyzed by several methods including GC-FID,
applications as fungicides; herbicides and pesticides, hydrazide drugs
GCNPD, HPLC, GC/MS, polarography, colorimetry, and iodometric
such asisoniazid, are, are used extensively to treat tuberculosis.
titrations. The iodometric method is simple and is used to measure
Hydrazine derivatives also find uses as azodyes, coupling agents in
hydrazine quantitatively in water at all concentrations. Hydrazine
colour photography, and as primers and explosives. A search for
reduces iodine to hydrogen iodide. Thus, an excess of standard
’hydrazine’ using the Scientific search engine Scirus yielded over two
solution of iodine is added to a measured volume of aqueous
th
thousand journal articles(as of January 24 2004) proving that
hydrazine solution and the excess iodine is back titrated at pH 7.0 to
hydrazine is still relevant in academia and worthy of interest.
7.2 (buffered by sodium bicarbonate) against a standard solution of
Hydrazine is colourless fuming liquid; with an ammonia like odour.
sodium hyposulfite using starch indicator. Hydrazine solutions may be
○ ○
It solidifies at 2 C and has a flashpoint at 52 C where it burns with a analyzed by various colorimetric methods. Low concentrations of
○
violet flame. Hydrazine has a viscosity of 0.876 centipoise at 25 C.It is hydrazine in aqueous samples at ppm level can be determined by
very soluble in water (it forms an azeotrope, 58.5% hydrazine: 41.5% treating the sample with an acidified solution of p-
water by molar composition, or 1.48%:28.52% by weight), the dimethylaminobenzaldehyde (PDMABA) and the absorbance of color
azeotrope with water boils at 120.5°C; forms hydrazine hydrate at 1:1 formed is measured at 485 nm with a spectrophotometer.
molar concentration in water. It is soluble in alcohols and other polar Hydrazine may be derivatized with salicylaldehyde to a hydrazone
solvents; pKa 8.1 at 25°C. derivative, separated on a suitable HPLC column and determined by a
Hydrazine is primarily produced using the Raschig synthesis UV detector.Aqueous samples may be directly injected into a polar GC
which involves the partial oxidation of ammonia or urea with an column interfaced to an FID. Anhydrous hydrazine may be
oxidizing agent usually hypochlorite but hydrogen peroxide and appropriately diluted in alcohol or ether and determined by GC/MS.
chlorine can be used instead. The reactions involved are as follows: The molecular ion for GC/MS determination by electron-impact
1
ionization is 32.
NH 3+ NaOCl NH 2Cl + NaOH
heat
EXPERIMENTAL
NH 2Cl + NH 3 + NaOH N2H 4 + NaCl + H2O
Exposure to hydrazine vapors or ingestion of the liquid can
N2H 4 + NaCl + H 2O
2NH 3 + NaOH cause nausea, vomiting, and convulsion. Direct contact can cause eye
.
damage. It also is a carcinogen; the maximum allowable exposure is
The initial reaction between ammonia and sodium hypochlorite is 3
0.01ppm or 0.1 mg/m .Hydrazine will explode if exposed to nitric acid
fast however the second step in the reaction process requires heating
or most oxidizing agents, a pure liquid hydrazine is potentially unstable.
○
above 120 C.The chloramines formed can reduce the product
The qualitative test for hydrazine using Hydrazine Sulfate and sodium
hydrazine to Nitrogen gas.
hydroxide is explosive if heated (silver fulminate). Hydrazine sulfate is
moderately toxic. Symptoms of ingestion are paresthesia, somnolence,
2NH2Cl + N2H4 2NH4Cl + N2 nausea, and vomiting. It also is an irritant to the eye. It is a confirmed

3. Table 1.0:The Reactions of Hydrazine

4. 2
carcinogen and an experimental teratogen. Chlorine is highly toxic the minutes, then washed with alcohol and recrystallized from water. The
-3. 5, 6
maximum allowable exposure is 0.5ppm or 1.5mg m product was allowed to dry then weighed the following week.
The product was tested qualitatively to determine if it was indeed
hydrazine sulfate using six test tubes containing a 3% solution of the
product. The first test tube was tested using acidified KMnO4. The
second test tube was tested using acidified CuCl2,the third test tube
was tested using acidified AgNO3,the fourth test tube was tested using
AgNO3/NH3.The fifth test tube was tested using Ferric Chloride
followed by a few drops of potassium hexaferrocyanate.The sixth test
tube was tested using Benzaldehyde followed by NaOH .
The confirmatory tests were followed by the Titrimetric analysis, a
standard 0.05 M solution of KIO3 was prepared by accurately weighing
2.67g KIO3 and making up to the mark in a 250ml volumetric flask
using distilled water.0.12 g of the hydrazine sulfate was placed in
Erlenmeyer flasks, then 20 ml H2O followed by 20ml concentrated HCl
and 4 ml Methylene chloride was placed in each flask. This
hydrazinium solution was titrated using the previously prepared primary
standard.
Figure 1. Chlorine generating apparatus
Results
Equipment
NH 3+ NaOCl NH 2Cl + NaOH
1. 5X 250ml Erlenmeyer flasks
heat
2. Chlorine generating apparatus(fig 1.0)
NH 2Cl + NH 3 + NaOH N2H 4 + NaCl + H2O
3. 7X Test tubes
4. 2x 50ml Burette
N2H 4 + NaCl + H 2O
5. 2x watch glass 2NH 3 + NaOH
6. 2x250ml Volumetric flask
7. Ice bath
I. Preparation of Gelatin
Reagents
Mass of gelatin = 2.5g
Volume of H2O added = 50ml
1. Potassium Permanganate powder
2. Sodium Hydroxide pellets
II.Preparation of NaOCl
3. Crushed Ice
4. Concentrated Hydrochloric Acid(12M)
Mass of NaOH = 15.12g
5. Concentrated Sulfuric Acid(16M)
Relative molar mass of NaOH = 40.0g
6. Concentrated Ammonia(15M) -1 -1
Number of moles of NaOH = 15.12g/40.0gmol = 3.78x 10 moles
7. Potassium Iodate
-2 3
8. Methylene chloride Volume of H2O added = 70ml = 7x 10 dm
9. Benzaldehyde -2 3
-1
Molar concentration NaOH(aq) = 3.78x 10 moles/ 7x 10 dm
10. Iron trichloride -3
=5.4 moles dm
11. Potassium hexacyanoferrate
12. Gelatin Mass of KMnO4= 7.0g
-1
Relative molar mass of KMnO4= 158.032 gmol
-1 -2
Number of moles of KMnO4 =7.0g/158.032 gmol = 4.429x10 moles
Procedure
-3
Molar concentration HCl = 12.0 moles dm
-2 3
Gelatin was prepared by dissolving 2.5g of powdered gelatin in Volume of HCl used = 40.0 ml = 4.0 x 10 dm
50ml of H2O.NaOCl was then prepared by weighing approximately 15g -2 3 -3
Number of Moles of HCl = 4.0 x 10 dm x12.0 moles dm
of NaOH and dissolving it in 70ml of H2O.7g of KMNO4 was weighed
and placed in the round bottom flask .The separatory funnel was filled
These values are certain, but it is assumed that not all the Cl2 evolved
with concentrated hydrochloric acid and the apparatus was set up as
shown in figure 1.The HCL was allowed to drip slowly until the KMnO4 is absorbed by NaOH(aq); therefore these values are irrelevant in
was discoloured(indicating total conversion of Mn(VII) to Mn(II).The determining the concentration of NaOCl and the subsequent
NaOCl solution generated was kept under alkaline(pH~7.5-9.0) concentration of hydrazine. Ammonia is assumed to be the limiting
○
conditions at 0 C. reagent. The relevant equation is therefore:
140ml of concentrated NH3 (33%, specific gravity 0.91) was - -
↓ N2H4 + Cl + H O
2 NH3 + OCl 2
added to the gelatin solution. This mixture was allowed to equilibrate to
an ice bath temperature. The prepared NaOCl solution was gradually
added to the gelatine/NH3.The reaction mixture was then allowed to 2 moles of Ammonia yields 1 mole of Hydrazine
○
-1 3
stand at 60-65 C for 25 minutes. The volume of the reaction mixture Volume of NH3 used = 14.0 x 10 dm
was carefully reduced from 150 ml to 50 ml, then cooled to room -3
Molar concentration of NH3 = 15 moles dm
temperature and filtered .The filtrate was cooled in an ice bath for 30 -1 3 -3
Number of moles of NH3 used = 14.0 x 10 dm x 15 moles dm
minutes to allow the insoluble salts to precipitate. It was filtered again.
=2.100 moles
Concentrated H2SO4 (10ml/100ml of solution) was slowly added to the
This implies that the maximum molar yield of hydrazine formed was
reaction mixture. The mixture was allowed to stand in ice for 15~20
2.100 moles/2 = 1.05 moles

5. 3
Hydrazine was extracted as the sulfate:
→
2NH3 + NaOCl NH2NH2 + H2O + NaCl 0.1230
Mass transferred(g)
→
NH2NH2 + H2SO4 NH2NH2 •H2SO4
Mole ratio N2H4 : N2H5(HSO4) is 1:1
Preparation of Standard 0.05 M KIO3
Therefore maximum molar yield of hydrazine sulfate is 1.05 moles
-1
Relative molar mass hydrazine sulfate = 130.125 g mol
Standard Mass of Mass Mass of Molar
Maximum theoretical yield = 1.05 moles x 130.125 g
number watchglass after Concentration
KIO3
-1
mol
Transfer In 250 ml
+ KIO3 (g)
2
Transferred
=1.366 x 10 g
volumetric
Actual yield = 3.77g (g) (g) flask /M
2
Percentage yield of Hydrazine sulfate =3.77g/1.366 x 10 g x 100 -2
39.9073 37.0413 2.8660
1 5.214 x 10
= 2.759%
III Qualitative Analysis of Product
-2
39.8304 37.0412 2.7892
2
Test Observations 5.394 x 10
KMnO4 was decolourized with
1. Acidified KMnO4
slight effervescence
2. Acidified CuCl2
No visible reaction
3. Acidified AgNO3
Solutions 1 to 4 were made by adding 20 ml distilled water,20 ml HCl
No visible reaction
4.Ammonaical AgNO3 and 4ml Methylene chloride to samples 1 to 4.These samples titrated
using the primary standard solutions of Iodate:
The solution remained colourless
5.FeCl3/K3Fe(CN)6
on addition of FeCl3but turned
→
-
dark green on addition of 2- +
IO3 + N2H6 N + 6H + 4e-
2
K3Fe(CN)6
Titrant KIO3 (.05214 M)
Two immiscible layers formed, the
6.Benzaldehyde NaOH
organic layer is the denser layer.
A white precipitate is formed on Solution Initial Volume Final Volume Volume of
addition of HCl and the organic Number of KIO3 /ml of KIO3 /ml KIO3 titrated
layer became buoyant /ml
1 0.33 14.44 14.11
2 14.44 27.43 12.99
Titrant KIO3 (.05394 M)
Titrimetric Analysis of Product
Solution Initial Volume Final Volume Volume of
46.6743
Mass of watchglass+
Number of KIO3 /ml of KIO3 /ml KIO3 titrated
NH2NH2 •H2SO4 (g)
/ml
3 5.52 16.42 10.09
46.5545
Mass after transfer
4 14.44 28.18 11.76
of sample 1 (g)
0.1198
Mass transferred (g) Calculations
46.4335
Mass after transfer of Solution Volume of Molar Number of
number Concentration moles of
sample 2 (g) KIO3 titrated
-
of KIO3 IO3 titrated
/ml
0.1210 -4
1 14.11 0.05214
Mass transferred (g) 7.35 x10
-4
2 12.99 0.05214 6.773 x10
46.312
Mass after transfer of
-4
3 10.09 0.05394
sample 3 (g) 5.443 x10
-4
4 11.76 .05394 6.343 x10
0.1223
Mass transferred(g)
46.1882
Mass after transfer of
sample 4 (g) The mole ratio of IO3:N2H6 is 2:1

6. 4
Number of Mass of Mass of Percentage
Solution Number of
moles of Hydrazine Sample/g Of hydrazine in
number moles of
- N2H4 in sulfate sample as sulfate
IO3
-2
sample /%
/10 g
titrated
-4
/10 moles
-4
1 3.675 4.782 0.1198 39.92
7.35 x10
-
2 4.407 0.1210
3.387 36.42
6.773 x10
4
-
3 3.542 0.1223
2.722 28.96
5.443 x10
4
-
4 4.128 0.1230
3.172 25.79
6.343 x10
4
DISCUSSION
The necessary precautions were taken in this experiment, the
chlorine generating apparatus was placed under the fume hood and
hydrazine was monitored as it was being evaporated.
The Raschig synthesis was a relatively fast process it took just over
two hours in laboratory. The yield was low but this can be attributed to
the fact that the chlorine gas evolved was not totally absorbed into the
NaOH solution and as a result the hypochlorite yield was low.
The product gave positive results when tested using the Wolff-
Kishner reduction of Benzaldehyde, and positive results when tested
using the metal hydrazine redox reactions. It converted ferrous iron to
ferric iron which was detected by ferrocyanate.
CONCLUSION
The Raschig synthesis was a relatively fast synthesis, but gave a
low yield of low purity
REFERENCES
1.Pradyot, P. Handbook of Inorganic Chemicals, 2002, McGraw-
Hill p.342-351
2. Pitt M J, Bretherick’s Handbook of Reactive Chemical Hazards Sixth
Edition—Volume 2, 1999 Butterworth-Heinemann Ltd, p.367
4. Dean John A., Lange’s Handbook of Chemistry Fifteenth Edition,
1999 McGraw-Hill, p11.925
5. Greenwood N.N., Earns haw A. (eds.) Chemistry of the elements
2ed. Elsevier, 1997.p427- 431

7. Laboratory and Pre Laboratory Questions
(Non ACS /Journal Format)
1. The hydrazine content of water is determined analytically at ppm level
by treating the sample with an acidified solution of dimethylaminobenzaldehyde
then the absorbance of the compound formed is measured at 485nm with a
spectrophotometer. This entails obtaining analytical grade hydrazine sulfate and
PDMABA, constructing a calibration line by making solutions of known concentration of
hydrazine (using the maximum allowable exposure as the highest concentration, from the
EPA etc, a blank as the minimum ,and a few concentrations in between), then repeating the
procedure using the unknown sample. The concentration of hydrazine can be determined
by the position of the sample on the calibration line. It is an analytical procedure
calculations of error will also have to be taken, the sample will probably need to be spiked
with a known concentration then of hydrazine then analyzed again to confirm the results.
2. Hydrazine sulfate is practically insoluble in alcohol (0.04% at 25○C), recrystallisation
using ethanol is the best method to remove hydrazine sulfate from the mother liquor.
3. Hydrazine is a compact fuel, it ignites on contact with nitric acid to yield gaseous
products, the rate of reaction and the mole ratio of reactant to gaseous product is a good
indicator of thrust The major use (non-commercial) of anhydrous N2H4 and its methyl
derivatives MeNHNH2 and Me2NNH2 is as a rocket fuel in guided missiles, space shuttles,
lunar missions, etc. For example the Apollo lunar modules were decelerated
on landing and powered on blast-off for the return journey by the oxidation of a 1:1
mixture of MeNHNH2 and Me2NNH2 with liquid N204; the landing required some 3 tonnes
of fuel and 4.5 tonnes of oxidizer, and the relaunching about one- third of this amount.
Other oxidants used are 02, H202, HNO3, or even F2. Space vehicles propelled by
anhydrous N2H4 itself include the Viking Lander on Mars, the Pioneer and Voyager
interplanetary probes and the Giotto space probe to Halley's comet5.. The disadvantages of
hydrazine are due to its toxicity, and it’s price $7 per barrel(NASA estimates).It is used for
short ranged systems such as ballistic missiles and for maneuvering space craft(but not for
liftoff).Hydrazine is no longer the sole fuel for propulsion on the market, the majority of
the new fuels are cubanes which convert to a greater amount of gaseous product hence they
provide more thrust. These compounds are produced under great strain (steric) this strain
is released in combustion in the form large heat of combustion(Advances in Chemical
Propulsion Science to Technology,CRC Press)
4. The substitution of calcium hydroxide for sodium hydroxide has been done by Hak Ki
Lee. His results were “The yield is proportional to the mole-ratio of ammonia to available
chlorine in calcium hypochlorite and about 60% is obtained when the ratio is 20.
2. Agar-agar can be used as a catalyst and its proper concentration in the solution is
0.005%.
3. Proper concentration of available chlorine in the reaction solution is 0.23 mole/l.

8. 4. The most effective condition for the reaction is a temperature of 60-65○C. maintained
for 20-25 min.
5. The reaction takes place equally well in either an open or closed container.
6. When calcium hypochlorite is applied in place of sodium hypochlorite, the yield of
hydrazine is increased as much as 17%.
7. The yield of hydrazine is decreased by eliminating the suspension of Ca(OH)2 which
results from the use of calcium hypochlorite.
8. When Ca(OH)2 is added to Raschig process, the yield of hydrazine is raised normally.
9. The fact that some metal ions, such as Cu++, inhibit the formation of hydrazine was
proved.
10. The suspension of Ca (OH)2 acted as a remarkable adsorbent for Cu++ like gelatin.
The suspension of Ca(OH)2 which results from the use of calcium hypochlorite acts as a
catalyst, absorbing metal ions, to increase the yield of hydrazine. So I think that calcium
hypochlorite is a more efficient oxidant than sodium hypochlorite in hydrazine syntheses”
Journal of the Korean Chemical Society
Volume 5, Number 1 (1961)
5.The yield of hydrazine can be improved by redesigning the chlorine generating
apparatus, to make use of small aspirators similar to those used in aquariums. This
increases the surface area over which chlorine is exposed to sodium hydroxide, giving
many tiny bubbles instead of many large bubbles, increasing the rate of formation of
hypochlorite. When ammonia is added the yield of hydrazine will be increased. The
apparatus could also be redesigned to recycle the chlorine gas to the reaction flask after it
has evolved. Catalysis could probably be achieved using a non metal such as activated
charcoal or any other medium for adsorption.
Pre Lab Questions
1.The original equation needed two moles of hydrogen ions, three moles of water on the
product side and a 2 moles Cl- to be balanced:
N2H4 + IO3- + 2Cl-+2H+↔ N2 + ICl2- +3H20
2. Hydrazine can bind to a metal such as Tungsten or molybdenum as a bidentate ligand
(Side on coordination).

9. NH
ArenediazoniumX
η−(C5H5)2WH2 η−(C5H5)2W X
MeOH/MePh(-20oC)
N
H(H)R
0 oC
NH
η−(C5H5)2W
X
N
R
It can also act as a bridging ligand as in ( {(W(NPh)Me3}2(µ-η1,η1-NH2NH2)µ---η2η2-
NH-NH):
Adapted from Chemistry of The elements modified using Chemoffice,Chemsketch,and Argus Labs)

10. 3.Hydrogen has oxidation number +1 always except in hydrides, Oxygen has oxidation
number -2 except in the peroxides ,and fluorine has oxidation number -1 always, nitrogen
has oxidation numbers, 3, –2, –1, 0, +1,+2, +3, +4 and +5 but favours–3, + 5, +4, +3, +2,
+1.For any compound without a charge,∑ oxidation numbers =0,therefore:
Compound Oxidation Number Of Nitrogen
N2H4 -3
NH3 -3
NF3 +3
N2 0
HNNH -1
NO +2
NO2 +4
N2O4 +3
NH2OH -1
CH3CN -3
4.Metal ions are removed from solution by gelatin in the laboratory synthesis of hydrazine.
Metal ions could also be removed by using EDTA or another chelating agent then filtering
the solution.EDTA(or any ligand which can displace a hydrazine ligand) is added in excess
then the solution can be filtered using a Buchner funnel to remove the chelated metal.