Organic chemistry
Watch a intro video2 resources
▶ YouTube
Video series
Crash Course Organic Chemistry
50 episodes of sophomore-level organic chemistry - nomenclature stereochemistry reaction mechanisms spectroscopy and synthesis. One of the most complete free video series on the subject.
⬡ Website
Video series
Problem sets & exercises
Organic Chemistry - Khan Academy
Comprehensive organic chemistry covering structure bonding nomenclature stereochemistry substitution elimination addition and carbonyl reactions with built-in practice.