Tshuaj thaj chaw ntawm alkanes

Methane thiab nws homologs hu ua txwv (nyeem) paraffinic hydrocarbons los yog alkanes. Qhov kawg-npe hu organic tshuaj (muaj cov kev tshuaj mis CnH2n + 2, uas qhia kev tsuas xyaus ntawm cov molecules, atoms uas yog txuas los ntawm covalent bonds yooj yim carbon-hydrogen los yog cov pa roj carbon-carbon) yog muab nyob rau hauv raws li cov thoob ntiaj teb Nomenclature tshuaj tebchaw. Lawv muaj ob lub ntsiab qhov chaw: crude roj thiab cov nkev. Thaj chaw ntawm alkanes nyob rau hauv ib tug homologous series nrog nce nyob rau hauv molecule tooj ntawm cov pa roj carbon atoms tsis tu ncua hloov.

Tus thawj plaub mej zeej ntawm lub homologous series tau dabneeg tsim npe. Hydrocarbons los, qab lawv yog denoted los ntawm Greek numerals xaus -Tus. Tus txheeb ze molecular yuag ntawm txhua successive hydrocarbon txawv los ntawm lub yav dhau los ib tug los ntawm 14 amu Lub zog ntawm alkanes, xws li melting point (solidification) thiab kub (hws), cov kev ceev thiab cov refractive index nce nrog ua molecular ceeb thawj. Nrog methane butane - gases nrog pentane ntawm pentadecane-kua, ua raws li los ntawm cov khib nyiab. Tag nrho cov waxes yog sib zog tshaj dej thiab tsis yaj nyob rau hauv nws. Rau alkanes muaj xws li:

• CH4 - methane;
• C2H6 - ethane;
• C3H8 - hluav taws roj zeb;
• C4H10 - butane;
• C5H12 - pentane;
• C6H14 - hexane;
• C7H16 - heptane;
• C8H18 - octane;
• C9H20 - nonane;
• C10H22 - Dean;
• C11H24 - undecane;
• C12H26 - dodecane;
• C13H28 - tridecane;
• C14H30 - tetradecane;
• C15H32 - pentadecane;
• C16H34 - hexadecane;
• C17H36 - heptadecane;
• C18H38 - octadecane;
• C19H40 - nonadecan;
• C20H42 - eicosane thiab thiaj li nyob.

Tshuaj thaj chaw ntawm alkanes muaj tsawg yam kev ua si. Qhov no yog vim tus kwv tij lub dag lub zog ntawm qhov uas tsis yog-polar C-C thiab tsawg-C-H bonds, thiab saturation ntawm lub lwg me me. Tag nrho cov atoms yog kev cob cog rua ntawm ib σ-bonds uas yooj yim ua kom puas vim hais tias ntawm lawv cov uas tsis muaj polarizability. Kev sib tawg ntawm lawv muaj peev xwm nkaus xwb yuav pom tau hais nyob rau hauv tej yam tej yam kev mob, lub radicals yog tsim, uas yog cov npe ntawm cov paraffinic tebchaw nrog hloov kaw. Piv txwv li, hluav taws roj zeb - propyl (C3H7-), ethane - ethyl (C2H5-), methane - methyl (CH3-) thiab thiaj li nyob.

Tshuaj thaj chaw ntawm alkanes hais txog inertness ntawm cov tebchaw. Lawv yog cov tsis muaj peev xwm ntxiv tshua. Raug ntawm cov no yog cov ib tug hloov cov tshuaj tiv thaiv. Oxidation (combustion) tshwm sim xwb paraffinic hydrocarbons ntawm txhawb kub. Lawv yuav tsum tau oxidized rau alcohols, aldehydes thiab acids. Raws li ib tug tshwm sim kreginga (txheej txheem thermal cleavage ntawm hydrocarbons) ntau dua alkanes ntawm ib tug kub ntawm 450 rau 550 ° C tej zaum daim ntawv uas hydrocarbons nrog ib tug tsawg dua molecular ceeb thawj. Nrog lub nce ntawm lub thermal decomposition kub yog hu ua pyrolysis.

Tshuaj thaj chaw ntawm alkanes nyob ntawm seb tsis tsuas yog nyob rau hauv lub xov tooj ntawm cov pa roj carbon atoms nyob rau hauv lub molecule, tab sis kuj nyob rau hauv cov qauv. Tag nrho cov qub paraffins yuav tau muab cais (ib C atom yuav kev cob cog rua nrog tsis muaj ntau tshaj li ob carbon atoms) thiab iso-qauv (C atom yuav kev cob cog rua rau plaub tug C-atoms ntawm no molecule muaj ib tug spatial qauv). Piv txwv li, pentane, 2,2-dimethylpropane muaj tib lub molecular nyhav thiab cov tshuaj mis C5H12, tab sis cov tshuaj thiab lub zog lawv txawv: cov melting point rho tawm 129,7 ° C thiab rho tawm 16,6 ° C, 36,1 ° C boiling thiab 9,5 ° C, ntsig txog. Isomers yooj yim mus nkag rau hauv tshuaj tshua tshaj lub qub qauv ntawm cov hydrocarbons nrog tib tus naj npawb ntawm atoms C.

Raug tshuaj thaj chaw ntawm alkanes - ib tug hloov cov tshuaj tiv thaiv, uas muaj xws li halogenation los yog sulfonation. Cov tshuaj tiv thaiv ntawm cov tshuaj nrog paraffin los ntawm ib tug radical mechanism nyob rau hauv tus ntawm tshav kub los yog lub teeb generated chlorinated methane: chloromethane CH3Cl, dichloromethane CH2Cl2, CHCl3 trichloromethane thiab cov pa roj carbon tetrachloride CCl4. Thaum sulfonation alkanes nyob rau hauv UV teeb, sulfonyl chlorides yog tau: R-H + SO2 + Cl2 → R-SO2-Cl + HCl. Cov tshuaj yog siv nyob rau hauv surfactant ntau lawm.