Txawm hais tias alkanes tsis ua haujlwm, lawv muaj peev xwm tso tawm ntau lub zog thaum cuam tshuam nrog halogens lossis lwm yam dawb radicals. Alkanes thiab cov tshuaj tiv thaiv nrog lawv tau siv tas li hauv ntau qhov kev lag luam.
Alkanes qhov tseeb
Alkanes nyob hauv ib qho chaw tseem ceeb hauv cov organic chemistry. Cov qauv ntawm alkanes hauv chemistry yog C H 2n + 2. Tsis zoo li cov tshuaj tsw qab, uas muaj lub nplhaib benzene, alkanes suav tias yog aliphatic (acyclic).
Nyob rau hauv lub molecule ntawm ib qho alkane, tag nrho cov ntsiab lus txuas nrog ib daim ntawv cog lus. Yog li ntawd, pawg ntawm cov tshuaj no muaj qhov xaus "-an". Raws li, alkenes muaj ib daim ntawv cog lus ob, thiab alkynes muaj ib daim ntawv cog lus triple. Alcodienes, piv txwv li, muaj ob daim ntawv cog lus.
Alkanes yog saturated hydrocarbons. Ntawd yog, lawv muaj qhov siab tshaj plaws ntawm H (hydrogen) atoms. Tag nrho cov pa roj carbon atoms hauv ib qho alkane yog nyob rau hauv txoj hauj lwm sp3 - hybridization. Qhov no txhais tau hais tias alkane molecule yog tsim raws li txoj cai tetrahedral. Lub methane molecule (CH4) zoo li tetrahedron,thiab cov alkanes tseem tshuav muaj cov qauv zigzag.
Txhua C atoms hauv alkanes txuas nrog siv ơ - bonds (sigma - bonds). C-C bonds yog nonpolar, C-H bonds tsis muaj zog polar.
Properties of alkanes
Raws li tau hais los saum no, pawg alkane muaj kev ua haujlwm me me. Cov kev sib txuas ntawm ob C atoms thiab nruab nrab ntawm C thiab H atoms muaj zog, yog li lawv nyuaj rau rhuav tshem los ntawm kev cuam tshuam sab nraud. Txhua daim ntawv cog lus hauv alkanes yog cov ntawv cog lus, yog li yog tias lawv tawg, nws feem ntau ua rau radicals.
Halogenation ntawm alkanes
Vim yog cov khoom tshwj xeeb ntawm daim ntawv cog lus ntawm atoms, alkanes muaj nyob rau hauv kev hloov pauv thiab cov tshuaj tiv thaiv decomposition. Hauv kev hloov pauv hauv alkanes, hydrogen atoms hloov lwm cov atoms lossis molecules. Alkanes hnov zoo nrog halogens - cov khoom uas muaj nyob rau hauv pawg 17 ntawm lub sij hawm ntawm Mendeleev. Cov halogens yog fluorine (F), bromine (Br), chlorine (Cl), iodine (I), astatine (At) thiab tennessine (Ts). Halogens yog cov muaj zog oxidizing cov neeg ua haujlwm. Lawv hnov qab yuav luag txhua yam khoom los ntawm lub rooj ntawm D. I. Mendeleev.
Chlorination cov tshuaj tiv thaiv ntawm alkanes
Hauv kev xyaum, bromine thiab chlorine feem ntau koom nrog halogenation ntawm alkanes. Fluorine yog ib qho tseem ceeb heev - nrog rau nws cov tshuaj tiv thaiv yuav tawg. Iodine tsis muaj zog, yog li kev hloov pauv cov tshuaj tiv thaiv yuav tsis mus nrog nws. Thiab astatine yog qhov tsawg heev hauv qhov xwm txheej, yog li nws nyuaj rau sau nws txaus rau kev sim.
Halogenation cov kauj ruam
Txhua alkanes mus txog peb theem ntawm halogenation:
- Lub hauv paus ntawm txoj saw lossis pib. Hauv qabtshav ntuj, tshav kub, los yog ultraviolet hluav taws xob, cov tshuaj chlorine molecule Cl2 tawg ua ob yam dawb radicals. Txhua tus muaj ib qho tsis sib xws electron nyob rau hauv txheej txheej.
- Kev txhim kho lossis kev loj hlob ntawm cov saw hlau. Radicals cuam tshuam nrog methane molecules.
- Kev txiav tawm yog qhov kawg ntawm alkane halogenation. Tag nrho cov radicals pib ua ke nrog ib leeg thiab thaum kawg ploj mus.
Alkanes bromination
Thaum halogenating siab dua alkanes tom qab ethane, qhov nyuaj yog tsim ntawm isomers. Cov isomers sib txawv tuaj yeem tsim los ntawm ib yam khoom raws li kev ua haujlwm ntawm lub hnub ci. Qhov no tshwm sim los ntawm kev hloov pauv cov tshuaj tiv thaiv. Qhov no yog pov thawj tias txhua H atom hauv alkane tuaj yeem hloov pauv los ntawm cov dawb radical thaum halogenation. Lub complex alkane decomposes rau hauv ob yam khoom, qhov feem pua ntawm cov uas yuav txawv heev nyob ntawm seb cov tshuaj tiv thaiv tej yam kev mob.
Propane bromination (2-bromopropane). Nyob rau hauv cov tshuaj tiv thaiv ntawm halogenation ntawm propane nrog ib tug Br2 molecule nyob rau hauv lub siab ntawm kub thiab tshav ntuj, 1-bromopropane - 3% thiab 2-bromopropane - 97% raug tso tawm.
YBromation ntawm butane. Thaum butane yog brominated nyob rau hauv qhov kev txiav txim ntawm lub teeb thiab kub kub, 2% 1-bromobutane thiab 98% 2-bromobutane tawm los.
Qhov txawv ntawm chlorination thiab bromination ntawm alkanes
Chlorination feem ntau siv hauv kev lag luam. Piv txwv li, rau zus tau tej cov kuab tshuaj uas muaj ib tug sib tov ntawm isomers. Thaum tau txais lub haloalkanenyuaj rau kev sib cais ntawm ib leeg, tab sis nyob rau hauv kev ua lag luam qhov sib tov yog pheej yig dua li cov khoom ntshiab. Hauv chav kuaj, bromination yog ntau dua. Bromine tsis muaj zog tshaj li chlorine. Nws muaj tsawg reactivity, yog li bromine atoms muaj kev xaiv siab. Qhov no txhais tau hais tias thaum lub sij hawm cov tshuaj tiv thaiv, cov atoms "xaiv" uas hydrogen atom los hloov.
Qhov xwm txheej ntawm cov tshuaj chlorination
Thaum chlorinating alkanes, isomers raug tsim nyob rau hauv kwv yees li sib npaug ntawm lawv cov pawg loj. Piv txwv li, chlorination ntawm propane nrog ib tug catalyst nyob rau hauv daim ntawv ntawm ib tug nce nyob rau hauv qhov kub thiab txias mus rau 454 degrees muab peb 2-chloropropane thiab 1-chloropropane nyob rau hauv ib tug ratio ntawm 25% thiab 75%, feem. Yog tias cov tshuaj tiv thaiv halogenation tsuas yog siv los ntawm kev siv hluav taws xob ultraviolet, 43% ntawm 1-chloropropane tau txais, thiab 57% ntawm 2-chloropropane. Nyob ntawm seb cov kev mob tshwm sim, qhov piv ntawm cov isomers tau txais yuav txawv.
Qhov xwm txheej ntawm cov tshuaj tiv thaiv bromination
Raws li qhov tshwm sim ntawm cov tshuaj tiv thaiv bromination ntawm alkanes, yuav luag cov tshuaj ntshiab tau yooj yim tso tawm. Piv txwv li, 1-bromopropane - 3%, 2-bromopropane - 97% ntawm n-propane molecule. Yog li ntawd, bromination feem ntau yog siv nyob rau hauv lub chaw soj nstuam los ua ke ib yam khoom.
YSulfation of alkanes
Alkanes kuj yog sulfonated los ntawm kev hloov pauv radical. Rau qhov kev tshwm sim tshwm sim, oxygen thiab sulfur oxide SO 2 (sulphurous anhydride) ib txhij ua ntawm alkane. Raws li qhov tshwm sim ntawm cov tshuaj tiv thaiv, cov alkane hloov mus rau hauv alkyl sulfonic acid. Piv txwv ntawm butane sulfonation:
y+ O
2 +SO2 → CH3CH2CH2CH 2SO2OH
General formula rau sulfoxidation ntawm alkanes:
R―H + O2 + SO2 → R―SO2OH
YSulfochlorination ntawm alkanes
Thaum cov tshuaj sulphochlorination, es tsis txhob oxygen, chlorine yog siv los ua oxidizing tus neeg sawv cev. Alkanesulfonic chlorides tau txais los ntawm txoj kev no. Cov tshuaj tiv thaiv sulfochlorination yog ib txwm muaj rau tag nrho cov hydrocarbons. Nws tshwm sim ntawm chav tsev kub thiab tshav ntuj. Organic peroxides kuj tseem siv los ua cov catalyst. Xws li cov tshuaj tiv thaiv tsuas yog cuam tshuam rau theem nrab thiab thawj daim ntawv cog lus ntsig txog carbon thiab hydrogen atoms. Qhov teeb meem tsis ncav cuag tertiary atoms, raws li cov tshuaj tiv thaiv saw tawg.
Konovalov cov tshuaj tiv thaiv
Cov tshuaj tiv thaiv nitration, zoo li cov tshuaj tiv thaiv halogenation ntawm alkanes, ua raws li cov txheej txheem dawb-radical. Cov tshuaj tiv thaiv yog ua los ntawm kev siv cov dilute heev (10 - 20%) nitric acid (HNO3). Cov tshuaj tiv thaiv kab mob: raws li qhov tshwm sim ntawm cov tshuaj tiv thaiv, alkanes tsim cov tshuaj sib xyaw ua ke. Txhawm rau catalyze cov tshuaj tiv thaiv, qhov kub nce mus txog 140⁰ thiab ib txwm siv los yog siab ambient siab. Thaum lub sij hawm nitration, C-C bonds raug puas tsuaj, thiab tsis yog C-H xwb, nyob rau hauv sib piv rau yav dhau los kev hloov pauv. Qhov no txhais tau hais tias kev tawg yog tshwm sim. Qhov ntawd yog kev sib cais.
Oxidation thiab combustion tshua
Alkanes kuj oxidized raws li hom dawb radical. Rau paraffins, muaj peb hom kev ua haujlwm uas siv cov tshuaj tiv thaiv oxidative.
- Nyob rau theem roj. Yog litau aldehydes thiab qis cawv.
- Nyob rau theem ua kua. Siv thermal oxidation nrog ntxiv ntawm boric acid. Nrog rau txoj kev no, cov cawv ntau dua tau txais los ntawm С10 rau С20..
- Nyob rau theem ua kua. Alkanes yog oxidized los ua ke carboxylic acids.
Nyob rau hauv cov txheej txheem ntawm oxidation, cov dawb radical O2 tag nrho los yog ib nrab hloov cov hydrogen tivthaiv. Ua tiav oxidation yog combustion.
Cov alkanes kub kub zoo yog siv los ua roj rau thermal fais fab nroj tsuag thiab cov tshuab hluav taws xob sab hauv. Hlawv alkanes tsim hluav taws xob ntau heev. Complex alkanes tau muab tso rau hauv lub cav combustion. Kev sib cuam tshuam nrog oxygen hauv alkanes yooj yim tuaj yeem ua rau tawg. Asph alt, paraffin thiab ntau yam lubricants rau kev lag luam yog tsim los ntawm cov khoom pov tseg uas tshwm sim los ntawm kev cuam tshuam nrog alkanes.
