Intro to OC Flashcards
Why is sp bond stronger than sp2 and sp3
sp orbitals have the highest % of s character, which forms the shortest and strongest bond, effective orb overlap is the highest, thus strength of bond is highest
define isomerism, types of isomerism
same molecular structure, different structural formula(chain, positional, fn grp, cis-trans,enantiomerism)
criteria for cis trans
1) C-C bond must have restriction rotation of bond
2) 2 diff grps/atoms bonded to each C atom
3) rings: must have 8 or more carbon atoms to avoid ring strain
compare BP of cis and trans isomers
cis has ↑ BP than trans
-both molecules have SMS
-↑energy is req to overcome the pdpd int b/w polar cis molecules than the weaker idid b/w non polar trans molecules
compare MP of cis and trans isomers
trans has ↑ MP than cis
-both molecules have SMS
-trans molecule has a higher symmetry, can pack ↑ closely in its lattice structure than cis
-↑energy is req to overcome the ↑extensive idid int in trans molecule
calc max no. of stereoisomers(CT+enan)
2^(m+n),
m= no. of C=C that fulfils CT
n= no. of chiral centres
define enantiomerism
stereoisomers that are mirror images of eo and are non superimposable on eo
criteria for enantiomerism
1) has a non superimposable mirror image(do not give the same structure when placed on top of eo)
2) has no internal plane of symmetry
3) has a chiral centre
why is racemic mixture optically inactive
-equal proportions of + and - enantiomers
-both enantiomers rotate PPL in opposite directions by the same extent
-no overall effect on PPL
-optically inactive
what is meso compound
has more than 1 chiral centre and an internal plane of symmetry
total number of stereoisomers for meso compound
2^m -1
why is meso compound optically inactive
-internal plane of symmetry present
-each chiral carbon will rotate PPL by the same angle in different directions
-no net rotation of PPL
- optically inactive
