To determine the configuration (R or S) of chiral carbons C₁ and C₂ in the given molecule, we use the Cahn-Ingold-Prelog (CIP) priority rules. A chiral carbon has four different groups attached. Assign priorities to the groups based on atomic number (higher atomic number gets higher priority).

Step 1: Identify Chiral Carbons
C₁ and C₂ are both chiral carbons as each has four distinct substituents.

Step 2: Assign Priorities for C₁
For C₁ (carbon with Br attached):

Group 1: Br (highest priority, atomic number 35)
Group 2: CH₃ (carbon with H, H, H)
Group 3: CH₂Br (carbon with Br, H, H; compare second atom: Br vs H, so higher than CH₃)
Group 4: H (lowest priority, atomic number 1)

So priorities: 1: Br, 2: CH₂Br, 3: CH₃, 4: H.

Orient the molecule so that the lowest priority group (H) is away from you. The order of groups 1→2→3 is clockwise, which corresponds to R configuration.

Step 3: Assign Priorities for C₂
For C₂ (carbon with CH₂Br attached):

Group 1: Br (from CH₂Br, highest priority)
Group 2: CH₂Br (carbon attached to Br and C₁; first atom C, but second atom Br (atomic number 35) vs H (from CH₃) so higher priority)
Group 3: CH₃ (carbon with H, H, H)
Group 4: H (lowest priority)

Priorities: 1: Br, 2: CH₂Br, 3: CH₃, 4: H.

Orient with H away. The order 1→2→3 is clockwise, so R configuration.

Final Answer: Both C₁ and C₂ have R configuration. So, 1R, 2R.

Related Topics

Chirality and Stereoisomerism: Chiral carbons are carbons with four different groups, leading to non-superimposable mirror images (enantiomers). The R/S system is used to describe the absolute configuration around chiral centers.

Cahn-Ingold-Prelog (CIP) Rules:

Assign priorities based on atomic number (higher number = higher priority).
If same atom, compare next atoms in the chain.
Orient the molecule so the lowest priority group is pointing away.
Trace from priority 1 to 2 to 3: clockwise = R, counterclockwise = S.

Formulae

No specific formulae, but understanding atomic numbers and group priorities is key. For example: $Atomic number of Br > C > H$