Question

Molecule F (NMR) Cio H₂iBr

Complete the reaction filling in both boxes using the spectra for Molecule F ( C10H21Br)

Answer 1

Based on the spectra, molecule F is

1.01 1.06 1.06 1.75 3.41 2.24 Y 1.01 1.21 1.06 Br 5-bromo-2.2,6-trimethylheptane

9H, 1.06, s 1H, 2.24, m 2H, 1.75,9 2H,1.21, t 1H.3.41.4 6H. 1.01, d E PPM

Where q - quartet, m - multiplet, t - triplet, d - doublet, s - singlet

Complete Reaction is

+=+ (i) Hydrogenation Na/NH, or H /Lindlar's catalyst (ii) Hydrobromination HBr/H2O 2,2,5,5-tetramethylhex-3-yne 5-bromo-2.2.6-trimethylheptane

Step 1: Hydrogenation

2,2,5,5-tetramethylhex-3-yne react with Na in NH₃ gives trans-alkene whereas if H₂/Lindlar's catalyst is used for hydrogenation obtain cis-alkene as product.

Step 2: Hydrobromination

Addition of HBr to alkene leads to 3-bromo-2,2,5,5-tetramethylhexane due to presence of water, bromide ion removed and formed carbocation followed by formation of cyclopropane. Due to steric factor, cyclopropane ring cleaves in such a way that to obtain tertiary carbocation and attack of bromide ion give final product.

+-t thereunto X Hydrogenation X 2.2.5,5-tetramethylhex-3-yne 2.2.5.5-tetramethylhex-3-ene 3-bromo-2,2,5,5-tetramethylhexane 5-bromo-2,2,6-trimethylheptane