Introduction to Stereochemistry

STEREOCHEMISTRY Isomern Same molecular formula but different Properties] Structural isomert Same molecular formula but differcent Structure Steneo Somen Same molecular formula [ but different arrangem of atom/groups] Chain Isomert Position isomer functional isomer Metamer Tautomer Conformatimal isomer Geometrical isomer Configuration isomern optical Psomer * When Dame molecular formula reepresents two or more Compound which diffen in their arrangement in space of atoms or group, then these are Called Stereoisomer and the Phenomenon is called Stereo isomerism. These arce Catagorcised in to two typer. 1) Conformational isomerism (C-C) 2) Configurational isomerism (C=c.) Geometrical Isomerism :- Cis-Treans lisomerism When Bame molecular formula represents two Compound, which differ in the carercangements of atorm or group around C=C, these are Called geometrica Isomerr and the Phenomenon is Called Geometrical isomerism. eg 2- Butene HC-CH=CH-CH (CH₃) H C=C H # When Bame group arce Present in Bame side of double bond, then the is omere is Called as Cis-Isomert. # When same group are present in different side of double bond, then the isomen is Called as trans-isomer. (Cis) (Cth) H H C=C (Trans) (Trans) eg. 1,2-dichlorto ethene H CI C=C-Cl (Cis) CI HC=CH 1 CI 1 CI Condition- 1. The compound must Contain a double bond. i.e C=C, CN. 2. Each double bonded Carton atom must be bonded to two different atom/groups. Geometrical isomen of Ketoxime and Aldoxime :- (Syn-Anti Isomerism) E-Z Notation:- These notation is applied to geometrical isomen in which all the atoms one groups bonded to C=C arcs differrent. The Structural requirement for E-2 Notation is- C=C E→ Entegen = Different 2- Zussamen = Together (6) A To specify the compound by Steps should be followed- E-z notation, following Step-1 (Selection of Priority order) The Priority Orden Belected between two atorm groups is as follow:- a) Highert atomic no. ot 1st atem bonded to double bonded Carbon will be assigned highern Priority. b) If the is atoms are the same, then Priority is determined by Comparing the and atom or even the third atom. c) If the ist atom or group bonded to double bonded Carbos) atom are isotope of one anothere, then atom with higher mass no. get higher Priority. d) If the ist atom is bonded to the and atom by multiple bond, then it is assume that the atom is bonded to that many no. of atom equal to its bond order. Step-I If two groups bonded to each double-bonded Carbon atom have the same Priority, then the Isomer is assigned a Z-notation, and if they are opposite each other, then the Isomer is assigned an E-issaunotation. D-L Nomencleatrere :- It is known that tve on -ve Bign relates with the nature of rotation of PPL of a Particular isomen. tve sign stands for Dextico (Right) where as -ve sign Stands fore Laevo (Left). This nomencleature is only valid for Compound Containing-OH group. If-on group of lowest Car Chiral Carbon is Present in left side of the molecule, then it is L-isomen Where as if it is Present is right side of the molecule, it is Called D-isomert. Projection Formela:- It is a method of representing the three-dimensional Structure of a molecule on a two-dimensional surface, called the Projection formula. There are three types of Projection formula. a) Fischere Projection formula 6) Newmann Projection formula c) Sawliorse Projection formula a) Fischen Projection Formula :- Let us Consider the Structure of Lactic acid. COOH Figing wedge formula of Lactic acid (C) Sawhorse Projection Formula:- →The bond between two Carbon atorm drawn as a straight line Slightly tilted to the right. →The freont (arben is shown as the lower left hand 15 Carbon where as the back Carbon "Thown as the Upperr right hand Carbon. Let us Consider the structure of n-butane.