Some of the molecules listed here have a chirality center;some do not. Write three-dimensional formulas for both enantiomers of those molecules that do have a chirality center.

Question

(a). 2-Fluoropropane
(b). 2-Methylbutane
(c). 2-Chlorobutane
(d). 2-methyl-1-butanol
(e). trans-2-butene
(f). 2-bromopentane
(g). 3-methylpentane
(h). 3-methylhexane
(i). 2-methyl-2-pentene
(j). 1-chloro-2-methylbutane

Answer 1

To identify which of the molecules have chirality centers, let's first outline the known chirality centers:

1. A chirality center (also called a chiral center or stereogenic center) generally refers to a carbon atom that is attached to four different substituents, leading to non-superimposable mirror images (enantiomers).

Now, let's examine the molecules directly:

Chirality Centers Present:

• (c) 2-Chlorobutane: Has a chirality center at the 2nd carbon.
• (d) 2-methyl-1-butanol: Has a chirality center at the 2nd carbon.
• (f) 2-bromopentane: Has a chirality center at the 2nd carbon.
• (j) 1-chloro-2-methylbutane: Has a chirality center at the 2nd carbon.

No Chirality Centers Present:

• (a) 2-Fluoropropane: No chirality center.
• (b) 2-Methylbutane: No chirality center.
• (e) trans-2-butene: No chirality center.
• (g) 3-methylpentane: No chirality center.
• (h) 3-methylhexane: No chirality center.
• (i) 2-methyl-2-pentene: No chirality center.

Three-Dimensional Representations:

For the molecules with chirality centers, enantiomers can be represented using wedge-dash notation, where solid wedges represent bonds coming out of the plane towards the viewer, and dashed wedges represent bonds going behind the plane.

(c) 2-Chlorobutane

1. (R)-2-Chlorobutane:

      Cl
       |
H3C - C - H
       |
      CH3

2. (S)-2-Chlorobutane:

      Cl
       |
H3C - C - H
       |
      CH3

(Note: The images are text representations. In a proper drawing, the spatial arrangement would be clearly depicted via proper wedge/dash conventions.)

(d) 2-Methyl-1-butanol

1. (R)-2-Methyl-1-butanol:

      OH
       |
H3C - C - H
       |
      CH3

2. (S)-2-Methyl-1-butanol:

      OH
       |
H3C - C - H
       |
      CH3

(f) 2-Bromopentane

1. (R)-2-Bromopentane:

      Br
       |
H3C - C - H
       |
      CH2CH3

2. (S)-2-Bromopentane:

      Br
       |
H3C - C - H
       |
      CH2CH3

(j) 1-Chloro-2-methylbutane

1. (R)-1-Chloro-2-methylbutane:

      Cl
       |
H3C - C - H
       |
      CH3

2. (S)-1-Chloro-2-methylbutane:

      Cl
       |
H3C - C - H
       |
      CH3

Note:

For specific three-dimensional structures of these compounds, it may be beneficial to use molecular modeling software or reference materials with three-dimensional diagrams, as the text-based representation has limitations. For accurate enantiomer identification (R/S configuration), experimental or computational methods like Cahn-Ingold-Prelog priority rules should be applied.