Why alkynes do not show geometrical isomerism ?

Why monocarboxylic acids do not show positional isomerism ?

Which type of octehedral complexes show geometrical isomerism ?

Square planar complexes of MX_(2)L_(2) type with coordination number of 4 exhibit geometrical isomerism whereas tetrahedral complexes with similar composition do not. Why? Justify the formation of a low spin complex and a high spin complex taking the examples of [Fe(CN)_(6)]^(3-) and [FeF_(6)]^(3-) on the bases of "crystal field splitting energy". (Delta_(0))

Which of the following compounds will exhibit geometrical isomerism ?

Which of the following can not show linkage isomerism ?