an example of Alkyl halides is R-X ( x represents any halogen)

C2F4 is Teflon it is an example of Alkyl Halides

it is C6H5-R , R = any alkyl group.

Depending on the desired definition of the word "contaminant" Alkyl Benzene Sulfonate is more likely the answer. Linear Alkyl Sulfonates are far more readily biodegraded than Alkyl Benzene Sulfonate due to their relative chemical structures. Alkyl Benzene Sulfonate can cause issues in waterways such as eutrophication, which in turn can lead to algal blooms.

the synthesis of alkyl fluorides by heating an alkyl chloride or alkyl bromide in the presence of a metallic fluoride like AgF, Hg2F2, CoF2 or SbF2.

An alkyl phosphate is any ester derived from an aliphatic alcohol and phosphoric acid.