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1,1 substitution &1,2 substitution takes place only in compounds with more than two carbon(here ''C" an example) atoms .
1,1 substitutions means substituting any atom in the first carbon atom in the compound(numbering of carbon is based on IUPAC rule)
2,2 substitution means substituting any atom adjacent to the first carbon atom
EXAMPLE1,1 SUBSTITUTION
CH3-CH2-CH2-Br reacts with NaCn gives CH3-CH2-CH2-CN + NaBr (fast reaction)
Here, Br atom is in the first C atom and that C atom is numbered as FIRST carbon C) atom.The adjacent to the first C atom is the second and so on....
Here the reagent NaCn ,Nais +ve and CN is in the -ve state moreover the CN-is highly electronegative than Br atom
substitution is based on number of factors
1.the electronegativity of the substituting agent
2.the stereo chemistry of the main group
3.steric hinderence of any group associated with the main group
4.electrophile or nucleophile present in the main chain.
5.presents of leaving group
there are two types of substitution
1.ELECTROPHILIC SUBSTITUTION
2.NUCLEOPHILIC SUBSTITUTION
ie, Aromatic or Aliphatic substitution reactions
these2 subsitutions give us isomers, molecules with identical type and number of atoms, but different arrangmennt.
1,1 is when the new atoms are added to the same atom
1,2 is when the new atoms are added to adjacent atoms
the atom is usually a carbon
this is related mostly to the electronegativity of the reacting molecules, and their arrangment hence the steric hindrance.
other types include1,3 -1,4 -2,3 -2,4.. and many more
counting usually starts at the double bond
the1,1 subtitution indicate that the two element are substituted in carbon number one
the1,2 subtitution indicate that the substitution is hapened one element in carbone number one the other in carbone number two
such us the notification of the number of carbone in an organic product is with international convensatin
