1@ Pritish
ya isotopes was the word I was looking for,I always forget terminologies
We all know that a chiral carbon is one attached to four diferent
groups.
1.Suppose in a compound CH2Cl2 the two hydrogen atoms are isotopes protium and tritium,and two chlorine atoms are
isotopes 35.5,37 will we say that is is chiral and opticaly active??
2.What if compund is chloro methane with three different isotopes of
hydrogen?Will the compound be optically active?
ANSWER ONLY IF YOU ARE SURe...
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17 Answers
11molecule can be meso also,if it has 2 stereogenic centres
Always true criteria is molecule should be devoid of symmetries
plane,centre and alternate axis of symmetry and then it will definitely show optical isomerism
1@ raja
as I already mentioned
One more imp statement
Stereogenic Centre is neither necessary nor sufficient condition for molecule to show optical activity
1But optical isomerism and chirality - basically they have no relationships.
I think for chirality, u just need 4 diff groups, thats all.
1Is the final conclusion that both CH2CL2 and chloromethane with different isotopes are optically active?
wat I can make out of this is both CH2Cl2 and Chloromethane with diffrent isotopes are optically active
CH2Cl2 is optically active according to the question and we have to confirm that which is not the case
but now I think I understood wat he was asking,maybe diffrent isotopes was for both the molecules,then ya optically active both
39CH2Cl2 by your own admission is optically active akshay...here the H groups are isotopes and the Cl groups are isotopes also!
1Is the final conclusion that both CH2CL2 and chloromethane with different isotopes are optically active?
39Bhai chirality ke conditions are not limited to having 4 different groups on a carbon atom...waise optical isomerism mein groups ke priorities are decided by their atomic numbers. So I don't think that even if isotopes were present, they would be chiral..there would be a conflict of priorities.
Besides, the other condition for chirality is being non-superposable on the mirror image. Since the groups are effectively the same with only a minor mass difference, there shouldn't be any optical activity..
Yes, had the group been bulky I could've said that due to steric factors optical activity is achieved(atropisomers).
1Allenes and Spiranes also ony when a is not equal to b on both sides
hope u get that
39http://en.wikipedia.org/wiki/Cahn%E2%80%93Ingold%E2%80%93Prelog_priority_rules
Yeah here they are!
"If two groups are isotopes, mass numbers are used to decide the priority"
Then they would be chiral.
Optical isomers which do not have chiral centres but are optically active(due to steric factors and being non-superposable on mirror image) are called atropisomers.
1Can you provide an example of a optically active comp without
stereogenic centre?
39Yeah I mentioned the stereogenic part in the second line...non-superposability is the main condition. Are you sure it will be chiral?
1Pritesh
waise optical isomerism mein groups ke priorities are decided by their atomic numbers
not completely true,for atoms with same atomic number(naam yaad nahi aa raha kya bolte hai unhe)they are decided on basis of Atomic mass,so it will be chiral
One more imp statement
Stereogenic Centre is neither necessary nor sufficient condition for molecule to show optical activity