Yuav ua li cas yog hydrogen daim ntawv cog lus? Lub hom feem

Yuav ua li cas yog hydrogen daim ntawv cog lus? Tag nrho cov paub cov piv txwv ntawm no kev twb kev txuas yog zoo tib yam dej (H2O). Vim lub fact tias cov pa atom (O) yog xav paub ntau electronegative tshaj ob hydrogen atom (H), nws cia li nkaum kiag cov zoo li ntawm cov hydrogen atoms tsevneeg electrons. Lub tsev lag luam ntawm xws li ib tug covalent ncov qaumteb qabteb daim ntawv cog lus tsim dipole. Pa atom acquires tsis loj heev tsis zoo xwb thiab cov hydrogen atoms - ib tug me me zoo xwb, uas yog attracted rau lub electrons (cov leeg khub ntawm lawv) nyob rau hauv cov pa atom uas nyob ib sab H2O molecules (i.e., dej). Yog li, peb yuav hais tias cov hydrogen daim ntawv cog lus - ib txoj kev ntawm lub zog ntawm attraction ntawm lub hydrogen atom thiab ib tug electronegative atom. Ib qho tseem ceeb feature ntawm lub hydrogen atom yog hais tias nws cov losis tswvyim dabtsi nrog cov attraction ntawm cov electrons nws yuav khaws cov tub ntxhais (i.e., proton, tsis muaj lwm yam electrons shielded). Txawm hais tias hydrogen daim ntawv cog lus yog weaker dua covalent, hais tias nws ua rau ib tug tag nrho series ntawm anomalous thaj chaw ntawm H2O (dej).

Feem ntau cov feem ntau, qhov no daim ntawv cog lus yog tsim nrog lub atoms ntawm cov nram qab no hais: oxygen (O), nitrogen (N) thiab fluorine (F). Qhov no tshwm sim rau yog vim li cas hais tias cov atoms ntawm cov ntsiab tseem me me nyob rau hauv loj thiab muaj lub siab electronegativity. C atoms ntau dua size (S leej faj los yog tshuaj Cl) Cov ntaub ntawv ib tug hydrogen daim ntawv cog lus yog weaker, txawm lub fact tias los ntawm lawv cov electronegativity cov khoom yog piv rau N (i.e. nitrogen).

Nws muaj ob hom ntawm hydrogen bonds:

1. Hydrogen intermolecular daim ntawv cog lus - tshwm sim ntawm ob tug molecules, piv txwv li: methanol, ammonia, hydrogen fluoride.
2. intramolecular hydrogen daim ntawv cog lus - tshwm sim nyob rau hauv ib zaug xwb molecule, xws li 2-nitrophenol.

Tsis tas li ntawd tam sim no nws yog ntseeg hais tias cov hydrogen tshuaj daim ntawv cog lus yog tsis muaj zog thiab muaj zog. Lawv txawv los ntawm txhua lwm yam nyob rau hauv lub zog thiab daim ntawv cog lus ntev (kev ncua deb ntawm atoms):

1. Hydrogen bonds uas tsis muaj zog. Zog - 10-30 kJ / mol, qhov nyiaj ntev - 30. Tag nrho cov tshuaj teev saum toj no yog cov piv txwv ntawm ib txwm los yog tsis muaj zog hydrogen daim ntawv cog lus.
2. Hydrogen bonds muaj zog. Zog - 400 kJ / mol, ntev - 23-24. Cov ntaub ntawv tau los ntawm kws, qhia tau tias muaj zog bonds yog tsim nyob rau hauv cov nram no ions: ib tug ion-vodoroddiftorid [FHF] -, ion-hydrated hydroxide [HO-H-OH] -, ion oxonium hydrated [H2O-H-OH2] + raws li zoo raws li ntau yam lwm yam organic thiab inorganic tebchaw.

Cawv ntawm hydrogen-linking

Anomalous qhov tseem ceeb ntawm boiling ntsiab lus thiab melting enthalpies ntawm vaporization thiab tus nto nro ntawm ib co ntawm cov tebchaw yuav ntaus nqi rau lub xub ntiag ntawm hydrogen bonds. Dej muaj anomalous qhov tseem ceeb ntawm tag nrho cov khoom, hydrogen fluoride thiab ammonia - boiling point thiab melting. Dej thiab hydrogen fluoride nyob rau hauv lub khoom thiab kua xeev vim lub muaj nyob rau hauv lawv ntawm hydrogen intermolecular bonds pom tau hais tias yuav polymerized. Qhov no kev sib raug zoo piav tsis tau tsuas yog siab dhau heev lawm melting kub ntawm cov ntaub ntawv, tab sis kuj ntawm lawv tsis muaj kev ceev. Wherein li melting hydrogen daim ntawv cog lus cov collapses, vim uas cov dej lwg me me (H2O) yog tau ntim ntau densely.

Lub dimerization ntawm tej yam tshuaj (carboxylic acid, e.g., benzoic thiab acetic acid) kuj tau piav los ntawm lub xub ntiag ntawm hydrogen tsevneeg. Dimer - ob molecules uas txuas ua ke. Vim li no, carboxylic acids boiling point siab tshaj uas ntawm tebchaw muaj kwv yees li tib yam molecular ceeb thawj. Piv txwv li, acetic acid (CH3COOH) lub kub kub yog 391 K, thaum acetone (CH3COCH3), nws yog 329 K.

Cawv ntawm hydrogen intramolecular bonds

Qhov no kev sib raug zoo kuj muaj feem xyuam rau cov qauv thiab cov thaj chaw ntawm ntau yam tebchaw, xws li 2- thiab 4-nitrophenol. Tab sis lub npe nrov tshaj thiab tseem ceeb piv txwv ntawm cov hydrogen daim ntawv cog lus - ib tug deoxyribonucleic acid (abbr.: DNA). Qhov no acid molecule daim ntau quav tso rau hauv ib ob helix, lub ob strands uas sib thooj los ntawm hydrogen bonds.