ORGANIC CHEMISTRY- I (NATURE OF BONDING AND STEREOCHEMISTRY)- SYMMETRY ELEMENTS AND OPERATIONS

ORGANIC CHEMISTRY- I (NATURE OF BONDING AND STEREOCHEMISTRY)- SYMMETRY ELEMENTS AND OPERATIONS ORGANIC CHEMISTRY- I (NATURE OF BONDING AND STEREOCHEMISTRY)- SYMMETRY ELEMENTS AND OPERATIONS

ORGANIC CHEMISTRY- I (NATURE OF BONDING AND STEREOCHEMISTRY)- CATENANES AND ROTAXANES

ORGANIC CHEMISTRY- I (NATURE OF BONDING AND STEREOCHEMISTRY)- CATENANES AND ROTAXANES

**Catenanes and roaxanes differ from all other organic compounds synthesized to this date in a way that molecular subunits are linked mechanically.

**Catenane is a compound consisting of two or more rings that are interlocked mechanically without there being necessarily any chemical interaction/bond between the two.

**Rotaxanes consist of a long, fairly linear molecule threaded through a macrocyclic ring, like cotton through the eye of a needle. ** Chemical topology deals with the structure and the property differences of compounds which are identical with regard to the aforementioned first three points and which in spite of that cannot be interconverted by conformational changes, such as rotation about an axis or modification of bond angles. In this module we have classified catenanes and rotaxanes according to their chemical topology.

** Stereochemistry of catenanes and rotaxanes is not a very highly explored topic except for discussion on simple structures of catenanes in particular. Rotaxanes have been very minimally dealt with in this area of study. In this module, we have discussed all possible cases of stereochemistry of catenanes and rotaxanes.

** Catenanes have been synthesized by incorporation of many functional units, including redox-active groups (e.g, viologen, TTF tetrathiafulvalene), photoisomerizable groups (e.g, azobenzene), fluorescent groups and chiral groups. Many of these units have been used to create mnolecular switches as described above, as well as for the fabrication of molecular electronic devices and molecular sensors.

** Rotaxane-based molecular machines have been of particular interest for their potential uses in molecular electronies as logical molecular switching elements and also as molecular shuttles.

 
ORGANIC CHEMISTRY- I (NATURE OF BONDING AND STEREOCHEMISTRY)- CATENANES AND ROTAXANES

ORGANIC CHEMISTRY- I (NATURE OF BONDING AND STEREOCHEMISTRY)- CYCLODEXTRINS – 2

ORGANIC CHEMISTRY- I (NATURE OF BONDING AND STEREOCHEMISTRY)- CYCLODEXTRINS – 2

**The cyclodextrins have a huge range of applications in varied areas of drug delivery and pharmaceutical industry because of their characteristic ability of complexation and other versatile characteristics.

** Cyclodextrins possess the ability to form inclusion Complexes with varied drug molecules by taking up a drug molecule in their cavity.

** The factors favouring complex formation are release of enthalpy rich water molecules from the cavity and other non-covalent interactions like electrostatic interactions, Van der Waal's interactions, hydrophobic interactions, hydrogen bonding, release of conformational strain and charge transfer interactions.

** Methods to monitor the physicochemical changes (like changes in conductance or pH etc.) occurring after the formation of inclusion complexes are applied to study the mentioned changes of the aqueous complexation media.

** We have thoroughly discussed how to increase the efficiency of formation of complexes.

** Non-conventional cyclodextrin complexes gain more importance in the aspects of drug solubilisation by means of molecular aggregation.

 
ORGANIC CHEMISTRY- I (NATURE OF BONDING AND STEREOCHEMISTRY)- CYCLODEXTRINS – 2

ORGANIC CHEMISTRY- I (NATURE OF BONDING AND STEREOCHEMISTRY)- CYCLODEXTRINS - 1

ORGANIC CHEMISTRY- I (NATURE OF BONDING AND STEREOCHEMISTRY)- CYCLODEXTRINS - 1

**Cyclodextrins first discovered by French scientist named A. Villiers, are known as structurally related group of naturally occurring products formed during bacterial digestion of cellulose.

** The glucopyranose having the chair conformation is the reason cyclodextrins have a truncated cone shape rather than perfect cylindrical shape.

** The physical state of all three cyclodextrins is crystalline and they exist as white powder. CDs donot have a sharp melting point, however they begin to decompose from temperatures 200 °C and above.

** Pharmaceutically important cyclodextrin derivatives encompass the hydroxypropy1 derivatives of beta and y-cyclodextrin. the randomly methylated Beta-cyclodextrin, sulfobutylether Beta-cyclodextrin, and the branched cyclodextrins such as glucosy1- Beta -

*** cyclodextrin.

** The most intriguing property of cyclodextrins is these molecules are able to form solid inclusion complexes also known as host-guest complexes with a very large range of solid, liquíd and gaseous compounds by following a molecular complexation protocol.

** The most widely known pharmaceutical application of cyclodextrins is their ability to enhance the stability, solubility, bioavailability and safety of drug molecules. 

** These characteristic properties of cyclodextrins or their derivatives make them appropriate for applications in analytical chemistry, the pharmaceutical industry, agriculture, in development of food flavours and toilet articles.


 
ORGANIC CHEMISTRY- I (NATURE OF BONDING AND STEREOCHEMISTRY)- CYCLODEXTRINS - 1

ORGANIC CHEMISTRY- I (NATURE OF BONDING AND STEREOCHEMISTRY)- BONDS WEAKER THAN COVALENT- ADDITION COMPOUNDS

ORGANIC CHEMISTRY- I (NATURE OF BONDING AND STEREOCHEMISTRY)- BONDS WEAKER THAN COVALENT- ADDITION COMPOUNDS

Supramolecular chemistry is a highly interdisciplinary field of science covering the chemical, physical, and biological feature of the organised chemical species of greater complexity than molecules themselves, which are held together and organized by means of intermolecular (non-covalent) binding interactions. 

**The energy of these non-covalent interactions is much smaller than 200-400 kJ mol¹ which is typical for covalent chemical bonds. 

**In addition to relatively strong ion-ion electrostatic interactions of ca. 100-350 kJ mol¹ and hydrogen bonding ca. 10-120 kJ mol¹, they include much smaller London dispersion forces, ion-induced dipole and dipole-dipole interactions that are in the range of 5-50 kj mol¹.

**The supramolecular chemistry generally concerns non-covalent bonding interactions.such as ion-ion interactions, ion-dipole interactions, dipole-dipole interactions hydrogen bonding, cation-π interactions, anion-π interactions, π-π interactions, closed shell interactions, van der Waals forces, crystal close packing and closed shell interactions. 

**The term 'non-covalent' encompasses an enormous range of attractive and repulsive effects.

  ORGANIC CHEMISTRY- I (NATURE OF BONDING AND STEREOCHEMISTRY)- BONDS WEAKER THAN COVALENT- ADDITION COMPOUNDS