intro to oc

• define stereoisomerism existence of 2 or more cmpds w same mol AND struct formula but diff spatial arrangement of atoms
• cis-trans condition 1. restricted rotation about a bond (dbl bond, ring struct) 2. for alkene: each C atom in C=C must be attached to 2 DIFF groups for cyclic cmpd: 2 or more C atoms in ring each attached to diff grps
• how cis-trans arise c=c cnt undergo free rotation unless pi bond broken, thus restricted rot abt c=c, two mols cnt interconvert spontaneously (2 distinct cmpds)
• do cis trans isomers have similiar chem and phy ppt? chem: sim phy: diff cis isomer

  higher bp: slightly higher polarity (idid AND pdpd, while trans only idid

  lower mp: packs poorly in lattice struct as 2 bulky methyl grps located on same side of mol, larger dist btwn mols, weaker imf
• define enantiomerism a cmpd displays enan if it forms a non-superimposable mirror image, such cmps are also known as chiral cmpds
• chiral cmpds features 1. no POS 2. usually one or more chiral centres
• mol w more than 1 chiral centre: max 2n stereoisomers if mol has x chiral centre & y dbl bond, max no. stereo is 2(x+y)
• eg. mol A has 4 stereoisomers, isomer 1 & 4 are not mirror images of eo and are called diastereomers
• meso cmpd 1. has more than 1 chiral centre BUT has POS 2. has mirror images that are superimposable 3. opt inactive
• electrophile: e- deficient species that is able to accept an e- pair from an e- rich atom, to form a cov bond

  may posses empty low-lying orb
• nucleophile: e- rich species that is able to donate an e- pair to an e- deficient atom, to form a cov bond
• cis alkene less stable than trans alkene why? steric strain (from repul of e clouds) arising from crowding btwn 2 alkyl grps in the cis isomer