Reserved

+  =  [] () //  

Arrows

→ (u+2192)  ⇄ (21C4)

Special symbols used in IUPAC names for organic compounds:

.  ,  -  {}  ′(prime/штрих, U+2032)

Superscript¹⁾

⁰ (u+2070)  ¹ (00B9)  ² (00B2), ³ (00B3), ⁴  ⁵  ⁶  ⁷  ⁸  ⁹  ⁺  ⁻  ⁼  ⁽  ⁾ (2074 – 207E)
˙ (u+02D9)  and Phonetic Extensions at u+1D00:  ᵢ 

Subscript

₀  ₁  ₂  ₃  ₄  ₅  ₆  ₇  ₈  ₉  ₊  ₋  ₌  ₍  ₎  (2080 – 208E)

Misc

∸ (2238) хотя по ИЮПАК пойдёт  ˙⁻