Lub Melting Point Ntawm Ib Alkane

Lub melting point ntawm cov khoom molecules kuj nce nrog nce ntawm cov pa roj carbon atoms, tab sis nws tsis yog li niaj zaus raws li qhov kev hloov ntawm boiling point, thiab tib series C 1-C3 tsis yog li ntawd, tab sis tus naj npawb ntawm carbon atoms. saum toj no C4 nce nrog nce. Qhov no yog vim hais tias lub zog ntawm crystal molecules nyob ntawm tsis tsuas yog nyob rau hauv tus txheeb ze molecular loj, tab sis kuj nyob rau hauv kev npaj ntawm molecules nyob rau hauv lub lattice. Qhov siab dua qhov molecular symmetry, qhov ze ntawm qhov kev npaj, qhov ntau dua qhov kev nyiam ntawm cov molecules, qhov siab dua qhov melting point. Nyob rau hauv ib txwm alkanes, lub melting point ntawm alkanes uas muaj khib carbon atoms nce tsawg tshaj li ntawm alkanes uas muaj txawm carbon atoms. Txawm nyob rau hauv lub melting point nkhaus ntawm ncaj-chain alkanes, alkanes nrog khib thiab txawm carbon atoms txhua tus tsim ib tug melting point nkhaus, nrog rau cov zauv nyob rau sab saum toj thiab khib tooj nyob rau hauv qab.
Los ntawm X-ray diffraction tsom xam, cov khoom siv n-alkane siv lead ua yog zigzag zoo, nrog ob pawg methyl ntawm ib sab hauv cov khib nyiab carbon toothed saw, xws li n-pentane. Cov pab pawg methyl ntawm ob qho kawg ntawm cov saw hlau tseem tsis nyob rau tib sab, xws li n-hexane, txawm tias cov saw hlau tseem nyob ze rau ib leeg, thiab cov kev sib cuam tshuam yog loj, yog li lub melting point nce tus nqi loj dua. qhov nce tus nqi ntawm cov kab lus carbon ib leeg.