The longest series of linked carbon atoms in a molecule is known as its carbon skeleton or carbon backbone.
ðə lˈɔŋɡɪst sˈɪɹiz ʌv lˈɪŋkt kˈɑːɹbən ˈæɾəmz ɪn ɐ mˈɑːlɪkjˌuːl ɪz nˈoʊn æz ɪts kˈɑːɹbən skˈɛlᵻtən ɔːɹ kˈɑːɹbən bˈækboʊn.