3+ Hydrogen Bond Examples : Detailed Insights And Facts


In this article we shall have a closer approach towards hydrogen bond examples :

Lets have a look at hydrogen bond examples :

AMMONIA


Occurrence.

Traces of ammonia occur in the air around the earth. It is produced in nature by the action of putrefying and ammonifying bacteria on nitrogenous organic matter, e.g., urine, etc.

hydrogen bond examples
hydrogen bond examples Ammonia

Image Credit : Wikipedia


Preparation


Ammonia may be prepared in the following ways :

  • By decomposing ammonium salts with caustic alkalis or lime, e.g.
  • By reducing nitrates or nitrites with Zinc and caustic soda.
  • Nitrates can be readily Reduced by alkalis and finely powdered Devarda’s alloy (50 parts Cu, 45 parts Al, 5 parts Zn).


Laboratory preparation of ammonia
Ammonia is prepared in the laboratory by heating ammonium chloride with slaked lime (in the ratio 1:3) In a hard glass test tube. The gas evolved is dried by passing through a tower packed with quicklime and collected by downward displacement of air. The gas being very soluble in the water cannot be collected over water. It can, however, be collected over mercury.

Ammonia reacts with sulphuric acid forming ammonium sulfate, with calcium chloride forming CaCl₂.8NH₃ and with phosphorus pentoxide giving NH₄PO₃.

Hence sulphuric acid, calcium chloride, or phosphorus pentoxide cannot be used for drying ammonia.

It can, however, be conveniently obtained in the laboratory by heating some liquor ammonia.

The first catalyst (finely divided iron with molybdenum as a promoter) is, however, widely used.


In Germany, a pressure of 200 atmospheres was employed at 720-770 K when the yield was 15 percent. This increased to 40 percent in the French Claude’s process, wherein the pressure of about 900 atmospheres was employed at the same temperature.


Impure gasses poison the catalyst; hydrogen and nitrogen used, therefore, must be very pure.

A mixture of nitrogen and hydrogen needed for the purpose is also manufactured by passing a mixture of water gas (CO + H2 ), producer gas ( N2 + CO), and steam over heated ferric oxide (catalyst) mixed with Cr2O3 (promoter) at 720 770 K. Carbon monoxide is oxidized by steam to carbon dioxide which is removed by washing the gas with water at 25 atmospheres pressure.

Excess of steam present reduces the equilibrium concentration of carbon monoxide to the minimum.

Removal of Catalyst Poisons.
Presence of Carbon dioxide, carbon monoxide, and traces of sulfur compounds (H2S) poison the catalyst. Removal of these catalytic poisons is, therefore, very essential. Carbon dioxide is removed, as stated above, by dissolution in water under 10-50 atmosphere pressure.

Carbon monoxide is removed by scrubbing the gas through an ammoniacal solution of cuprous formate or acetate, whereas hydrogen sulfide is removed by absorption in potassium hydroxide solution under pressure.

Haber process – for ammonia manufacturing

Image Credit : Textbook of inorganic chemistry by Sultan Chand and Sons

Process.
A diagrammatic sketch of the plant employed. Nitrogen obtained by liquefaction of air is mixed with 3 times its volume of pure dry hydrogen and compressed to 200-350 atmosphere pressure. The compressed mixture is passed over the catalyst maintained at about 725-775 K in an electrically-heated chamber.

The issuing gases containing about 10-20% of ammonia at a temperature of 375-475 K are cooled in a water cooler when some ammonia liquefies. The residual gases containing 6-7% ammonia are recycled. More ammonia may be condensed by refrigeration to 253 K when the residual gases contain only 1.2% ammonia. Alternatively, ammonia may be dissolved in water.

Ammonia is stored in steel tanks or vessels of cast iron, aluminum polythene, rubber, etc. It is transported in steel cylinders or tank wagons designed to withstand the vapor pressure of ammonia.
This is the cheapest and the most important method today for the manufacture of ammonia. A flow sheet for the Haber process is given in Fig. 2

Fig 2 Manufacturing ammonia

Image Credit : Textbook of inorganic chemistry by Sultan Chand and Sons

Tests for Ammonia

It has a characteristic pungent odor.
It turns moist red litmus paper blue and moist turmeric paper brown.

Uses of Ammonia

Hydrazine or Diamide, NH2-NH2.

Hydrazine ( among very important hydrogen bond examples ) is a hydride of Nitrogen which can be prepared as discussed below :

Hydrazine Molecule

Image Credit : Wikipedia

Raschig’s Method.
A very strong ( aqueous solution) that of ammonia is heated ( almost boiled ) along with hypochlorite ( even glue in little amount should be present)
Glue in-habits reactions yielding NHCl2 and NC3, possibly by removal of heavy metal ions which catalyze these reactions. The reaction occurs in two stages :

The oxidation state of the nitrogen atoms in the hydrazine molecule
is —2, hence the above reactions represent oxidation of ammonia.

In the process of distillation (fractional ), the obtained mixture of reaction contains hydrazine hydrate. The obtained solution is later cooled and is made to react with sulphuric acid( which is said to be sparingly soluble) and is separated out as crystals of the precipitate.

Anhydrous hydrazine may be prepared by treating hydrazine sulfate with liquid ammonia when
ammonium sulfate is precipitated almost quantitatively.

Ammonium sulfate is filtered off, and the excess of ammonia is
allowed to evaporate, leaving anhydrous hydrazine.

By Reducing Nitric Oxide.
We can prepare Hydrazine by the reaction of potassium sulfite ( which is saturated – along with nitric oxide and sodium amalgam.

Properties.

Physical.
Hydrazine is colorless in nature, having a boiling point of 386 K ( also said to be miscible in water). It is also observed that it is soluble in alcohol. One more thing about it is that it absorbs moisture(hygroscopic); therefore, care should be taken while handling it.

If the container is left open, it might contaminate the substance. The solution of hydrazine in water has a faintly alkaline reaction. It dissolves sulfur, selenium, phosphorus, and arsenic.

Chemical

Formation of Hydrate. It is very soluble in water from which a solid hydrate N2H4.H20 may be prepared but cannot be dehydrated.
Decomposition. On heating, hydrazine decomposes into ammonia and nitrogen.


Basic Nature. Hydrazine is a weak di-acid-base and can form salts with one or two equivalents of acid.

For example, hydrochloric acid gives two salts, viz, hydrazine monochloride, NH2.NH3Cl and hydrazine chloride, NH3CI. NH3Cl. Compounds of only the first type are common. These basic properties can be related to the presence of a lone pair of on each nitrogen atom.

Hydrazine molecule has an unsymmetrical structure in which the NH3 groups do not rotate freely. This is due to the tendency of the unshared electron pairs to get as far apart as possible.

Uses
Hydrazine is used as a reducing agent.
Hydrazine NH2NH2 and its derivative phenylhydrazine, C6H5NHNH2, are used as reagents in organic chemistry.
It is used as a fuel for rockets.

Read more about : Triple Bond Examples: Detailed Insights And Facts

Hydroxylamine, NH2OH.


It is a hydroxy hydride of nitrogen and is related to ammonia in the structure; it is generally discussed along with the hydrides of nitrogen. It was discovered by Lossen in 1895.

Hydroxylamine Molecule

Image Credit : Wikipedia

Preparation
By the Reduction of Nitric Oxide.

A stream of nitric oxide is passed through hydrochloric acid, to which a few pieces of tin are added. The nascent hydrogen liberated by tin and hydrochloric acid reduces nitric oxide to hydroxylamine, which remains in solution as hydroxylamine hydrochloride.

Tin is removed as sulfide by passing hydrogen sulfide, and the solution is filtered and evaporated to dryness. The residue of hydroxylamine hydrochloride is distilled with sodium methoxide in methyl alcohol when free hydroxylamine is obtained.

Sodium chloride is filtered off, and the methyl alcohol is separated by distillation under reduced pressure.


By the Reduction of Nitrous Acid.


A concentrated solution of sodium nitrite is mixed with a solution of sodium carbonate, and sulfur dioxide is passed into the solution till just acidic when the sodium salt of hydroxylamine disulphonic acid is produced.

The solution is now warmed with dilute sulphuric acid to 360 K when sodium hydroxylamine is hydrolyzed to hydroxylamonium bisulfate.

The free base may be isolated by the addition of a calculated quantity of baryta water when the combined sulphuric acid is precipitated as barium bisulfate.


Properties.


Physical.


Hydroxylamine is a white crystalline solid melting at 306 K and boils at 341 K at 20 mm pressure. It is almost in the liquid form in the air and is observed to be soluble in water ( also in alcohol and ether ).


Chemical


Stability – The oxidation state of N in NH2OH is – 1. It is very unstable and starts decomposing (auto-oxidation where oxidation number of two N-atoms of NH2OH is raised from – 1 to zero oxidation state in N2 and the other is lowered from-1 to -3 in NH3) into ammonia, nitrogen, and water even before its melting point is reached.


Action on Halogens

It explodes with halogens and reduces them to the corresponding hydracids.

It bromates and iodates to bromides and iodides, respectively


Uses:
It has got many uses, but in modern days it is used as a reagent ( in organic chemistry) for many reactions. ( especially for identifying Carbonyl compounds )

Read more about : 5+ Double Bond Examples: Detailed Insights And Facts

Hydrazoic Acid, N3H.

This is another important hydride of nitrogen, and unlike ammonia and hydrazine, it is acidic in nature.
Preparation.

Hydrazoic Acid Molecule

Image Credit : Wikipedia

Preparation

It may be obtained by the action of nitrous acid on hydrazine, or its salts, e.g., hydrazine chloride.

Properties

Physical

Hydrazoic acid is a colorless volatile liquid with a highly obnoxious odor. It is poisonous in nature. It explodes violently when beaten or struck. It is readily soluble in water and alcohol. It boils at 310 K and, when solidified, melts at 186 K.

Chemical

Reduction

Hydrazoic acid is reduced by sodium amalgam or finely divided platinum into ammonia or hydrazine.


Oxidation

Oxidizing agents, e. g. acidified potassium permanganate, etc., oxidize acid to nitrogen and water.

Read more about : Stereoselective vs Stereospecific: Detailed Insights and Facts

Problems

A chemical substance mentioned above that has a very strong odor and should not be taken directly can be very dangerous to health?

Ans Ammonia

A chemical substance mentioned above which is chiefly used in identifying of groups like carbonyl?

Ans Hydroxylamine

What is Devarda’s alloy?

Ans It consists of 50 parts of copper, 45 parts of Aluminum, and 5 parts of Zinc

Sania Jakati

This is Sania Jakati from Goa. I am an aspiring chemist pursuing my post graduation in organic chemistry. I believe education is the key element that moulds you into a great human being both mentally and physically. I'm glad to be a member of scintillating branch of chemistry and will try my best to contribute whatever I can from my side and Lambdageeks is the best platform where I can share as well as gain knowledge at the same time. LinkedIn-https://www.linkedin.com/in/sania-jakati-0954101bb

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