See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the chiral center and substituents of 2-fluorobutane. The chiral center is C2, bearing four different groups: F, H, CH3 (C1), and CH2CH3 (C3-C4). Priority order by CIP rules: F (highest, 1) > CH2CH3 (2) > CH3 (3) > H (lowest, 4). Step 2 - Determine what configuration S requires. For S configuration, when the lowest priority group (H) is pointing away from the viewer, the remaining three groups (F > CH2CH3 > CH3) must be arranged in a counterclockwise (CCW) direction. Step 3 - Analyze option (c). In option (c), the wedge-dash drawing shows: H on top (plain/in-plane bond going up), C-F on the right (plain/in-plane bond going right), H3C on a hashed wedge (going back/away from viewer), and CH2CH3 on a bold wedge (coming toward viewer). Wait - re-reading the image: H3C has the hatched wedge (dashes going back) and CH2CH3 has the bold wedge (coming forward). So H is in the plane (top), F is in the plane (right), H3C is going back (dashed wedge), CH2CH3 is coming forward (bold wedge). Step 4 - Assign configuration in option (c). The lowest priority group is H, which is in the plane pointing up. To assign configuration, we look at the arrangement of F (1), CH2CH3 (2), CH3 (3) with H pointing up (partially toward viewer on one side). Using the standard method: since H is not pointing directly away, we determine the rotation of 1->2->3 and then correct. With H pointing upward (roughly toward viewer from standard perspective), if the rotation F->CH2CH3->CH3 appears clockwise (CW) in the drawing, we invert to get the actual configuration = CCW = S. In option (c): F is to the right, CH2CH3 is on the bold wedge (forward/down-left area), CH3 is on the dashed wedge (back). Tracing F(right)->CH2CH3(bold wedge, forward)->CH3(dashed, back) gives a counterclockwise rotation as seen. Since H points upward (toward viewer), we invert: actual rotation = CW = ... Re-evaluating: in option (c) H is on a plain bond going up (in the plane of paper). F is on a plain bond going right (in plane). H3C is on a hashed/dashed wedge (going away from viewer). CH2CH3 is on a bold wedge (coming toward viewer). With H in the plane pointing up, it is neither toward nor away. Using the swap method: imagine rotating so H points away. The priorities 1(F, right), 2(CH2CH3, bold-forward), 3(CH3, dashed-back) - tracing these in the projected view when H is sent away gives a CCW (counterclockwise) arrangement = S configuration. This matches (S)-2-fluorobutane. Step 5 - Why other options fail. Option (a) shows no stereochemistry. Option (b) has H3C on the dashed wedge and CH2CH3 on the bold wedge with F on top and H on the right - this arrangement gives R configuration. Option (d) is a cross/sawhorse-like flat representation that does not clearly specify S stereochemistry and represents a different spatial arrangement corresponding to R. Therefore, the correct answer is C.