Alkanes, lossis paraffinic hydrocarbons, yog qhov yooj yim tshaj plaws ntawm txhua chav kawm ntawm cov organic tebchaw. Lawv lub ntsiab yam ntxwv yog muaj nyob rau hauv lub molecule ntawm ib leeg xwb, los yog saturated bonds, li no lub npe - saturated hydrocarbons. Ntxiv rau cov roj thiab roj uas paub zoo, alkanes kuj pom muaj nyob hauv ntau cov nroj tsuag thiab tsiaj cov ntaub so ntswg: piv txwv li, tsetse ya pheromones yog alkanes uas muaj 18, 39 thiab 40 carbon atoms hauv lawv cov chains; alkanes kuj pom muaj ntau nyob rau hauv lub sab sauv tiv thaiv txheej ntawm cov nroj tsuag (cuticle).
cov ntaub ntawv dav dav
Alkanes yog nyob rau hauv chav kawm ntawm hydrocarbons. Qhov no txhais tau hais tias tsuas yog carbon (C) thiab hydrogen (H) yuav muaj nyob rau hauv cov mis ntawm tej compound. Qhov txawv tsuas yog tias txhua daim ntawv cog lus hauv cov molecule yog ib leeg. Lub valence ntawm carbon yog 4, yog li ntawd, ib tug atom nyob rau hauv ib tug compound yuav yeej ib txwm raug khi rau plaub lwm atoms. Tsis tas li ntawd, tsawg kawg ib daim ntawv cog lus yuav yog hom carbon-carbon, thiab tus so tuaj yeem yog carbon-carbon thiab carbon-hydrogen (hydrogen valency yog 1, yog li xav txog hydrogen-hydrogen bonds.txwv). Raws li, cov pa roj carbon atom uas tsuas muaj ib daim ntawv cog lus C-C yuav raug hu ua thawj, ob C-C daim ntawv cog lus - theem nrab, peb - tertiary thiab plaub, los ntawm kev sib piv, quaternary.
Yog tias koj sau cov qauv molecular ntawm txhua alkanes hauv daim duab, koj tau txais:
- CH4,
- C2H6,
- C3H8.
thiab lwm yam. Nws yog ib qho yooj yim los ua ib tug universal formula uas piav qhia txog ib qho kev sib xyaw ntawm cov chav kawm no:
CH2n+2.
Qhov no yog cov qauv dav dav rau paraffinic hydrocarbons. Cov txheej txheem ntawm txhua qhov ua tau rau lawv yog homologous series. Qhov txawv ntawm ob tug neeg nyob ze ntawm koob yog (-CH2-).
Alkanes nomenclature
thawj thiab yooj yim tshaj plaws nyob rau hauv cov kab saturated hydrocarbons yog methane CH4. Tom ntej no los ethane C2H6, muaj ob lub atoms carbon, propane C3H 8, butane C4H10, thiab los ntawm cov tswv cuab thib tsib ntawm homologous series, alkanes tau muab npe los ntawm cov pa roj carbon ntau. atoms nyob rau hauv lub molecule: pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane thiab hais txog. Txawm li cas los xij, ntau cov pa roj carbon monoxide tuaj yeem hu ua "ib zaug" tsuas yog tias lawv nyob hauv tib txoj kab sib txuas. Thiab qhov no tsis yog ib txwm muaj.
Daim duab no qhia ntau yam qauv uas nws cov qauv molecular zoo ib yam: C8H18. Txawm li cas los xij, peb muaj peb qhov sib txawv. Xws liQhov tshwm sim thaum muaj ntau yam qauv qauv sib txawv rau ib qho qauv molecular hu ua isomerism, thiab cov tebchaw hu ua isomers. Muaj ib qho isomerism ntawm cov pob txha pob txha ntawm no: qhov no txhais tau hais tias cov isomers txawv ntawm qhov kev txiav txim ntawm carbon-carbon bonds hauv molecule.
Txhua isomers uas tsis muaj cov qauv linear hu ua branched. Lawv cov nomenclature yog raws li cov kab txuas txuas ntev tshaj plaws ntawm cov pa roj carbon atoms hauv cov molecule, thiab cov "txoj hauj lwm" raug suav tias yog cov hloov pauv ntawm ib qho ntawm cov hydrogen atoms ntawm cov pa roj carbon los ntawm "lub ntsiab" saw. Yog li, 2-methylpropane (isobutane), 2, 2-dimethylpropane (neopentane), 2, 2, 4-trimethylpentane tau txais. Tus lej qhia tus lej carbon ntawm cov saw tseem ceeb, ua raws li tus lej ntawm cov khoom sib xws, tom qab ntawd lub npe hloov pauv, tom qab ntawd lub npe ntawm cov saw tseem ceeb.
Alkanes qauv
Txhua plaub daim ntawv cog lus ntawm carbon atom yog covalent sigma bonds. Txhawm rau tsim lawv txhua tus, carbon siv ib qho ntawm nws plaub lub orbitals ntawm lub zog sab nraud - 3s (ib thooj), 3p (peb daim). Nws xav tias txij li ntau hom orbitals tau koom nrog hauv kev sib txuas, ces cov txiaj ntsig yuav tsum sib txawv ntawm lawv cov yam ntxwv ntawm lub zog. Txawm li cas los xij, qhov no tsis tau pom - hauv methane molecule, tag nrho plaub yog tib yam.
Txoj kev xav ntawm hybridization yog siv los piav txog qhov tshwm sim no. Nws ua hauj lwm raws li nram no: nws yog assumed tias ib tug covalent daim ntawv cog lus, raws li nws yog, ob lub electrons (ib tug los ntawm txhua lub atom nyob rau hauv ib tug khub) nyob rau hauv raws nraim ntawm cov atoms khi. Hauv methane, piv txwv li, muaj plaub daim ntawv cog lus, yog li plaubkhub ntawm electrons nyob rau hauv ib lub molecule yuav tawm tsam ib leeg. Txhawm rau txo qhov kev thawb tas mus li no, lub hauv paus atom hauv methane npaj tag nrho plaub ntawm nws daim ntawv cog lus kom lawv nyob deb li deb tau. Nyob rau tib lub sijhawm, kom muaj txiaj ntsig ntau dua, nws, raws li nws tau, sib xyaw tag nrho nws cov orbitals (3s - ib qho thiab 3p - peb), tom qab ntawd ua plaub qhov zoo ib yam tshiab sp3-hybrid orbitals. tawm ntawm lawv. Yog li ntawd, "kawg" ntawm covalent bonds, nyob rau hauv uas hydrogen atoms nyob, tsim ib txwm tetrahedron, nyob rau hauv nruab nrab ntawm uas muaj carbon. Lub pob ntseg no hu ua sp3-hybridization.
Tag nrho cov pa roj carbon atoms hauv alkanes yog nyob rau hauv sp3-hybridization.
Lub cev muaj zog
Alkanes nrog cov roj carbon atoms ntawm 1 txog 4 - gases, los ntawm 5 mus rau 17 - kua nrog ib tug pungent tsw, zoo ib yam li cov pa roj av, saum toj no 17 - khib nyiab. Lub boiling thiab melting cov ntsiab lus ntawm alkanes nce raws li lawv molar loj (thiab, raws li, tus naj npawb ntawm carbon atoms nyob rau hauv lub molecule) nce. Nws yog tsim nyog hais tias nyob rau tib lub molar loj, branched alkanes muaj noticeably qis melting thiab boiling ntsiab lus tshaj lawv unbranched isomers. Qhov no txhais tau hais tias cov ntawv cog lus sib txuas hauv lawv tsis muaj zog, yog li tag nrho cov qauv ntawm cov khoom tsis tshua muaj resistant rau sab nraud influences (thiab thaum rhuab, cov bonds tawg sai dua).
Txawm hais tias muaj qhov sib txawv, qhov nruab nrab, tag nrho cov alkanes tsis tshua muaj polar: lawv xyaum tsis yaj hauv dej (thiab dej yog cov kuab tshuaj polar). Tab sis lawv tus kheejunsaturated hydrocarbons los ntawm cov uas yog kua nyob rau hauv ib txwm tej yam kev mob yog nquag siv raws li tsis-polar solvents. Qhov no yog siv n-hexane, n-heptane, n-octane thiab lwm yam.
tshuaj muaj zog
Alkanes tsis ua haujlwm: txawm tias piv rau lwm cov tshuaj organic, lawv hnov mob nrog cov npe tsis tshua muaj cov tshuaj reagents. Yeej, cov no yog cov kev tshwm sim uas tshwm sim raws li lub hauv paus ntsiab lus: chlorination, bromination, nitration, sulfonation, thiab lwm yam. methane chlorination yog ib qho piv txwv classic ntawm cov tshuaj tiv thaiv kab mob. Nws lub ntsiab yog raws li nram no.
Ib qho tshuaj tiv thaiv kab mob muaj ntau theem.
- ua ntej, cov saw tau yug los - thawj cov dawb radicals tshwm sim (qhov no, qhov no tshwm sim nyob rau hauv qhov kev txiav txim ntawm photons);
- kauj ruam tom ntej yog kev txhim kho cov saw hlau. Nyob rau hauv cov chav kawm ntawm nws, cov tshuaj tshiab yog tsim, uas yog tshwm sim los ntawm kev sib cuam tshuam ntawm ib co dawb radical thiab ib tug molecule; qhov no tso tawm cov dawb radicals tshiab, uas nyob rau hauv lem react nrog rau lwm cov molecules, thiab hais txog;
- thaum ob lub dawb radicals sib tsoo thiab tsim cov khoom tshiab, cov saw tawg tshwm sim - tsis muaj cov dawb radicals tshiab tsim, thiab cov tshuaj tiv thaiv decays hauv ceg no.
Cov tshuaj tiv thaiv nruab nrab ntawm no yog ob qho tib si chloromethane CH 3Cl thiab dichloromethane CH2Cl2, thiab trichloromethane (chloroform) CHCl3, thiab carbon tetrachloride CCl4. Qhov no txhais tau hais tias radicals tuaj yeem tua leej twg: ob qho tib si methane nws tus kheej thiabCov khoom nruab nrab ntawm cov tshuaj tiv thaiv, ntau thiab ntau dua hloov hydrogen nrog halogen.
Cov tshuaj tiv thaiv tseem ceeb tshaj plaws rau kev lag luam yog isomerization ntawm paraffinic hydrocarbons. Nyob rau hauv lub chav kawm ntawm nws, lawv branched isomers yog tau los ntawm unbranched alkanes. Qhov no ua rau kom lub thiaj li hu ua detonation kuj ntawm lub compound - ib tug ntawm cov yam ntxwv ntawm automotive roj. Cov tshuaj tiv thaiv yog nqa tawm ntawm ib qho txhuas chloride catalyst AlCl3 ntawm qhov kub ib ncig ntawm 300oC.
Kev sib xyaw ntawm alkanes
Txij thaum lub tsev kawm ntawv theem pib, ntau tus tau paub tias cov organic compounds hlawv los ua dej thiab carbon dioxide. Alkanes tsis muaj kev zam; Txawm li cas los xij, hauv qhov no, lwm yam tseem ceeb dua. Cov cuab yeej ntawm paraffinic hydrocarbons, tshwj xeeb tshaj yog gaseous hydrocarbons, yog qhov tso tawm ntawm cov cua kub thaum lub sij hawm combustion. Yog vim li cas yuav luag tag nrho cov roj tseem ceeb yog tsim los ntawm paraffins.
Hydrocarbon raws cov zaub mov
Cov no yog cov seem ntawm cov kab mob uas muaj sia nyob thaum ub uas tau dhau los ntawm kev hloov pauv tshuaj mus ntev yam tsis muaj oxygen. Natural gas yog nyob rau nruab nrab 95% methane. Tus so yog ethane, propane, butane thiab me impurities.
Nrog roj, txhua yam nthuav ntau dua. Nws yog ib pawg ntawm cov chav kawm sib txawv tshaj plaws ntawm hydrocarbons. Tab sis qhov tseem ceeb yog nyob ntawm alkanes, cycloalkanes thiab cov tshuaj tsw qab. Paraffin hydrocarbons ntawm cov roj tau muab faib ua feem (uas suav nrog cov neeg nyob sib ze tsis txaus ntseeg) raws li tus lej ntawm cov pa roj carbon atoms hauv cov molecule:
- roj av (5-7С);
- roj av (5-11 C);
- naphtha (8-14 C);
- kerosene (12-18 C);
- roj av (16-25 C);
- roj - roj roj, roj hnub ci, roj nplua nyeem thiab lwm yam (20-70 C).
Raws li pawg neeg, cov roj crude mus rau ntau hom roj. Vim li no, hom roj (roj av, ligroin - tsheb laij teb roj, kerosene - dav hlau roj, diesel roj) coincide nrog cov fractional faib ntawm paraffinic hydrocarbons.
