IIT JEE , AIEEE Forum - Chemistry , Organic Chemistry - REACTION MECHANISM-3

zamuka

1.How is a compound named as D or L ? ( please explain in detail)

(rates assured)

zamuka

reply karo yaar!!

ashish_banga

The last chiral center in an aldose chain (farthest from the aldehyde group) was chosen by Fischer as the D / L designator site. If the hydroxyl group in the projection formula pointed to the right, it was defined as a member of the D-family. A left directed hydroxyl group (the mirror image) then represented the L-family. Fischer's initial assignment of the D-configuration had a 50:50 chance of being right, but all his subsequent conclusions concerning the relative configurations of various aldoses were soundly based. In 1951 x-ray fluorescence studies of (+) tartaric acid, carried out in the Netherlands by Johannes Martin Bijvoet (pronounced "buy foot"), proved that Fischer's choice was correct.
It is important to recognize that the sign of a compound's SPECIFIC ROTATION(an experimental number) does not correlate with its configuration (D or L). It is a simple matter to measure an optical rotation with a polarimeter. Determining an absolute configuration usually requires chemical interconversion with known compounds by stereospecific reaction paths.

zamuka

any1 who can explain in non bookish language??

ramkumar_november

you see a compound in fischer projection........ see the last but one carbon atom(the one above CH2OH)....... if OH is attached right to it .... the compound is D-......... else if OH is attached to left of it... the compound is L-.........

siva7792

The comp r classified into d&l forms on the basis of the fact that ---
in which direction the comp rotates the polar light beam

First of all verify whether the comp has chiral center
then figure out a fishermen projection
According to the preference order number the comp
if the numbers order comes in clock wise dir it is d-form
otherwise it is l-form
Pre ord... 1 is given 4 comp with high atomic no.
If the first case doesnt give the result{the same comp attached}
then go 4 2nd
If nth doesnt give refer n+1 th case
But the least prefered group should b at the bottom

ambareesh13

i suggest you to refer ncert class 12 part2
chapter carbohydrates

just basic

if the configuration of an element corresponds or is similar to that of glyceraldehyde ie lowest oxidation nmber carbon at the top and highest oxidation number carbon at the bottom ..... if CH2OH IS AT BOTTOM AND OH IS AT BOTTOM RIGHT it is assigned D else it is assigned L

chilbi.chillz

c its very simple

D - mean Dextro (right) rotation

L - means leavo ( left) rotatory

so wen v r given an optically active or inactive compound having a chiral centre , then v can check da rotation made by da compound. if it is towards left or right

we 'll give da preferences acc to da At. wt of da first grp attached to it

Basically it is frm H to OH

Like for eg in lactic acid

elastiboysai

chilbi
u r wrong,
wat is asked here is the
D or L (not d or l - the dextro and laevo as u said)
D or L is actually cnfiguring a compd relative to glyceraldehyde
any compd that hs a config simlar to d glyceraldehyde is calld D else L

ashish_banga

yes chilbi u are wrong

Ask & Discuss Questions with Community & Experts