What are "O-hydrocarbons"? A pharma translator's question (Russian to English, "О-углеводороды")

A translator colleague is translating from Russian a plan for study of a number of leachable and extractable substances (pharmacology). This Russian text mentions one particular class of chemicals which theoretically could become leachables: 



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> "Hydrocarbons (alkanes, alkenes, alkynes, **O-hydrocarbons**)". 
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She can't understand what this could mean.


The Russian term is **О-углеводороды**. 



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> [![enter image description here](https://i.stack.imgur.com/iUA81.png)](https://i.stack.imgur.com/iUA81.png)
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My fellow translator sent a letter to the authors, and they replied that they used this term to stand for "oxygen-substituted hydrocarbons", just like andselisk suggested. 


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