They are made by reacting hydrazines with ketones or aldehydes:
ð eɪ WORD_BOUNDARY ɑ ɹ WORD_BOUNDARY m eɪ d WORD_BOUNDARY b aɪ WORD_BOUNDARY ɹ ɪ æ k t ɪ ŋ WORD_BOUNDARY h aɪ d ɹ eɪ z iː n z WORD_BOUNDARY w ɪ ð WORD_BOUNDARY k ɛ t oʊ n z WORD_BOUNDARY ɔ ɹ WORD_BOUNDARY æ l d ɪ h aɪ d z WORD_BOUNDARY