Question

(2S,4S)-4-chloro-4-fluorobutan-2-ol & (2R,3S)- 3ethyl-2-methoxyhexane How do I go about drawing the structural formula for these two ?

Answer 1

To draw the stereo-structural formula of the given compounds first we are to draw their structural formulae .

Compound -I

The structural name=> 4-chloro-4-fluoro-2-butanol

• Its stem name `'but'` suggests that it has longest C- chain of 4- C-toms like this

`-stackrel(1)C-stackrel(2)C-stackrel(3)C-stackrel(4)C-`

• `'-2anol'` suffix tells the presence of an hydroxy group`(-OH)` at `C_2` and the compound is saturated one.

  `-stackrel(1)C-stackrel(2)C"(OH)"-stackrel(3)C-stackrel(4)C-`

• `'"-4-chloro-4-fluoro-"'` prefix name denotes the presence of one `Cl and` one `F` atom at position 4 of the chain. Satisfying residual valencies of C-atoms by H-atoms we get the following structural formula of the compound-I
  `stackrel(1)CH_3-stackrel(2)color(red)CH"(OH)"-stackrel(3)CH_2-stackrel(4)color(red)CH"(Cl)(F)"`

Obviously this structural formula shows the presence of two chiral C-atoms at positions 2 and 4.

So the stereo structural formula of

(2S,4S)-4-chloro-4-fluoro-2-butanol is as follows

Compound -II

The structural name of thecompound is
3-ethyl-2-Methoxyhexane

• Its stem name `'hex'` suggests that it has longest C- chain contains 6 C-atoms

  `-stackrel(1)C-stackrel(2)C-stackrel(3)C-stackrel(4)C-stackrel(5)C-stackrel(6)C-`

• `"'-ane'"` suffix tells the compound is saturated one.

• `'"3ethyl-2-methxy"'` prefix name denotes the presence of one `OCH_3and` one `C_2H_5`groups at position 2 and 3 of the chain. Satisfying residual valencies of C-atoms by H-atoms we get the following structural formula of the compound-II
  `stackrel(1)CH_3stackrel(2)CH(OCH_3)stackrel(3)CH(C_2H_5)stackrel(4)CH_2stackrel(5)CH_2stackrel(6)CH_3`

Obviously this structural formula shows the presence of two chiral C-atoms at positions 2 and 3.

So the stereo structural formula of

(2R,3S)-3ethyl-2-methoxyhexane is as follows