Study notes - Hofmann rearrangement

Hofmann rearrangement, also known as Hofmann degradation and not to be confused with Hofmann elimination, is the reaction of a primary amide with a halogen (chlorine or bromine) in strongly basic (sodium or potassium hydroxide) aqueous medium, which converts the amide to a primary amine. For example:

Mechanism:

Applications:

Aliphatic & aromatic amides are converted into aliphatic and aromatic amines, respectively

In the preparations of anthranilic acid from phthalimide

Nicotinic acid is converted into 3-Aminopyridine

The symmetrical structure of α-phenyl propanamide does not change after Hofmann reaction.

Wacker process And Zeise's salt formation

The Wacker process refers to the oxidation of ethylene to acetaldehyde in the presence of palladium(II) chloride as the catalyst.

The net reaction can also be described as follows:

[PdCl4]2 − + C2H4 + H2O → CH3CHO + Pd + 2 HCl + 2 Cl−
This conversion is followed by reactions that regenerate the Pd(II) catalyst:

Pd + 2 CuCl2 + 2 Cl − → [PdCl4]2− + 2 CuCl
2 CuCl + ½ O2 + 2 HCl → 2 CuCl2 + H2O

Zeise's salt formation:

This compound is commercially available as a hydrate. The hydrate is commonly prepared from K2[PtCl4] and ethylene in the presence of a catalytic amount of SnCl2.

The alkene C=C bond is approximately perpendicular to the PtCl3 plane. In Zeise's salt and related compounds, the alkene rotates about the metal-alkene bond with a modest activation energy. Analysis of the barrier heights indicates that the π-bonding between most metals and the alkene is weaker than the σ-bonding. In Zeise's anion, this rotational barrier has not been assessed.

Wagner Meerwin rearrangement

The rearrangement involving in C skeleton through carbocation intermediate are collectively called as wagner meerwin rearrangement.

confirmations for ethane

18 Electron rule

18 electron rule is to account the stability of the organomettalic complex. 
It can be calculated by adding group number of central metal atom and total number of electron contribution of ligand atom.

 Eg:Cr(CO)6

6+2*6=18

Here central metal atom has the group number=6 and each CO ligand contribute 2 electron.

Metal Complexes also called as coordination complex is the chemical structure which contains central metallic atom, bonded with number of surrounding molecules are also called as ligands.
The atom in the ligand which is directly connected with metal atom is called as donaratom.


Applicability

The rule usefully predicts the formulae for low-spin complexes of the Cr, Mn, Fe, and Co triads. Well-known examples include ferrocene, iron pentacarbonyl, chromium carbonyl, and nickel carbonyl.

All metal complexes are not following 18 electron rules but there are some selected low spin metal complexes follow the this.

Ligands in a complex determine the applicability of the 18-electron rule.

Ligands are the atoms or molecules which bind the central atom to form coordination complexes. There are lots of applications of ligands in coordination chemistry and bio chemistry and applied biology.



Calculation methods:

Some other examples:

CO2

Carbon dioxide (chemical formula CO2) is a colorless gas with a density about 60% higher than that of dry air.

 Carbon dioxide consists of a carbon atom covalently double bonded to two oxygen atoms. 

It occurs naturally in Earth's atmosphere as a trace gas.

 Natural sources include volcanoes, hot springs and geysers, and it is freed from carbonate rocks by dissolution in water and acids.

 Because carbon dioxide is soluble in water, it occurs naturally in groundwater, rivers and lakes, ice caps, glaciers and seawater. 

It is present in deposits of petroleum and natural gas. Carbon dioxide is odorless at normally encountered concentrations.

Periodic table

This is a tabular arrangement of the chemical elements.

Elements are arranged by atomic number and electronic configurations.

Periodic table was developed by Dmitri Mendeleev in 1869.

 The periodic table can be used to derive relationships between the various element properties, and also to predict chemical properties and behaviours.

 The seven rows of the table, called periods(A period in the periodic table is a horizontal row. All elements in a row have the same number of electron shells.)

 Generally metals on the left and non-metals on the right.

 The columns, called groups( is a column of elements in the periodic table of the chemical elements), contain elements with similar chemical behaviours.

The modern periodic table now provides a useful framework for analyzing chemical reactions, and used in nuclear physics and other sciences.

 The elements from atomic numbers 1 (hydrogen) to 118 (oganesson) have been discovered or synthesized, completing seven full rows of the periodic table.

The first 98 elements all occur naturally, though some are found only in trace amounts and a few were discovered in nature.

 Elements 99 to 118 have only been synthesized in laboratories or nuclear reactors

Each chemical element has a unique atomic number (Z) representing the number of protons in its nucleus.

Most elements have differing numbers of neutrons among different atoms, with these variants being referred to as isotopes.

 For example, carbon has three naturally occurring isotopes: all of its atoms have six protons and most have six neutrons as well, but about one per cent have seven neutrons, and a very small fraction have eight neutrons. 

Isotopes are never separated in the periodic table; they are always grouped together under a single element.

In the standard periodic table, the elements are listed in order of increasing atomic number Z (the number of protons in the nucleus of an atom). 

 Lanthanides and actinides:

The lanthanide and actinide series make up the inner transition metals.

The lanthanide series includes elements 58 to 71, which fill their 4f sublevel progressively.

The actinides are elements 89 to 103 and fill their 5f sublevel progressively.

Actinides are typical metals and have properties of both the d-block and the f-block elements, but they are also radioactive.

Lanthanides have different chemistry from transition metals because their 4f orbitals are shielded from the atom’s environment.

The 14 elements (numbers 58 to 71) of the lanthanide series are also known as the rare earth elements. Most lanthanides are formed when uranium and plutonium undergo nuclear reactions. Atomic bombs charged with plutonium (actinoid) were used in World War II