Polypropene chain features tetrahedral carbon geometry

Steps:

• Polypropene forms from propene via addition polymerization, creating a saturated hydrocarbon chain.
• The repeating unit is -[CH₂-CH(CH₃)]-, with all backbone carbons bonded to four single bonds.
• These carbons are sp³ hybridized, adopting tetrahedral electron geometry.
• Tetrahedral geometry dictates C-C-C bond angles of 109.5° throughout the chain.

Why A is correct:

• sp³ hybridized carbons in alkanes and saturated polymers like polypropene follow VSEPR theory, resulting in tetrahedral 109° bond angles.

Why the others are wrong:

• B: 120° angles indicate sp² hybridization with double bonds, absent in polypropene's saturated chain.
• C: 90° angles do not occur in organic carbon chains; they suggest octahedral or other geometries not applicable here.
• D: All 120° implies a planar, conjugated system like in aromatic polymers, but polypropene is aliphatic and non-planar.

Final answer: A