XII. AXIT HỮU CƠ (AXIT CACBOXILIC; ACID CARBOXILIC)

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  • Gio khoa ha hu c Bin son: V Hng Thi

    208

    XII. AXIT HU C (AXIT CACBOXILIC; ACID CARBOXILIC)

    XII.1. nh ngha Axit hu c l mt loi hp cht hu c m trong phn t c cha nhm COOH (nhm cacboxyl, ) XII.2. Cng thc tng qut Axit hu c: R(COO)n R: Gc hirocabon ha tr n, c th l H, c th l khng (zero,0) n: nguyn, 1 (n = 1: Axit hu c n chc n 2: Axit hu c a chc) CxHy(COOH)n n 2 x 0 CxHy + n y + n 2x + 2

    y 2x + 2 n

    Axit hu c n chc: R-COOH (R: Gc hirocacbon ha 1, c th l H) CxHy-COOH x 0 CxHy + 1 y + 1 2x + 2

    y 2x + 1 CnH2n + 2 2k 1COOH CnH2n 1 2k COOH (n 0 ; k = 0, 1, 2, 3, 4,.) CnH2n + 2 m 1 COOH CnH2n + 1 - mCOOH n 0 m: 0; 2; 4; 6; 8; CnH2n mO2 n 0 m: 0; 2; 4; 6; 8; Axit hu c n chc no mch h: CnH2n + 2 1COOH CnH2n + 1COOH (n 0) CnH2nO2 (n 1) R-COOH (R: Gc hirocacbon ha tr 1, no mch h, c th l H)

    C O HO

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    Bi tp 99 Vit cng thc tng qut c mang nhm chc ca cc cht sau y: a. Axit hu c n chc no mch h. b. Axit hu c n chc. c. Axit hu c n chc, cha mt lin kt i C=C trong phn t, mch h. d. Axit hu c cha hai nhm chc axit, no, mch h. e. Axit hu c n chc, cha mt nhn thm trong phn t, ngoi nhn thm cc gc

    hirocacbon cn li ch gm lin kt n mch h. f. Axit cacboxilic a chc (ba nhm chc axit), khng no (mt lin kt i C=C, mt

    lin kt ba CC), cha mt vng trong phn t. g. Axit hu c n chc no mch h c cha 18 nguyn t C trong phn t. Bi tp 99 Vit cng thc tng qut ca: a. Cht hu c ng ng axit acrilic. b. Axit hu c ng ng axit fomic. c. Cht hu c ng ng axit benzoic. d. Axit hu c ng ng axit tereptalic. e. Axit hu c ng ng axit oxalic. f. Cht hu c ng ng vi axit xiclohexancacboxilic. g. Axit hu c nh chc, cha mt lin i C=C, mch h. XII.3. Cc c tn (ch yu l tn ca axit hu c n chc no mch h) Ankan Axit ankanoic (Mch chnh l mch C cha nhm COOH v di nht, C ca COOH c nh s 1) Axit cacboxilic (Hu ht axit hu c c tn thng thng, nn thuc lng tn mt s cht thng gp) Th d: H-COOH Axit metanoic (CH2O2) Axit fomic CH3COOH Axit etanoic (C2H4O2) Axit axetic CH3CH2COOH Axit propanoic (C2H5COOH; C3H6O2) Axit propionic; Axit metylaxetic CH3CH2CH2COOH Axit butanoic (C3H7COOH; C4H8O2) Axit n-butiric; Axit etylaxetic CH3-CH-COOH Axit 2- metylpropanoic CH3 Axit isobutiric; Axit imetylaxetic (C3H7COOH; C4H8O2)

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    CH3CH2CH2CH2COOH Axit pentanoic (C4H9COOH; C5H10O2) Axit n-valeric CH3-CH-CH2-COOH Axit 3-metylbutanoic CH3 Axit isovaleric (C4H9COOH; C5H10O2) CH3CH2CH2CH2CH2COOH Axit hexanoic (C5H11COOH; C6H12O2) Axit caproic CH3CH2CH2CH2CH2CH2COOH Axit heptanoic (C6H13COOH; C7H14COOH) Axit enantoic CH3(CH2)6COOH Axit octanoic (C7H13COOH; C8H16O2) Axit caprilic CH3(CH2)7COOH Axit nonanoic (C8H17COOH; C9H18O2) Axit pelacgonic CH3(CH2)8COOH Axit ecanoic (C9H19COOH; C10H20O2) Axit capric Mt s axit bo (axit bo cao, gp trong cht bo, ch yu dng este vi glixerin) thng gp: C13H27COOH Axit miristic; Axit tetraecanoic C15H31COOH Axit panmitic; Axit hexaecanoic C17H35COOH Axit stearic; Axit octaecanoic C17H33COOH Axit oleic; Axit cis-9-octaecenonic C17H31COOH Axit linoleic; Axit cis, cis - 9, 12 - octaecaienoic C17H29COOH Axit linolenic; Axit cis, cis, cis 9, 12, 15 - octaecatrienoic Mt s axit hu c n chc khng no: CH2=CH-COOH Axit propenoic; Axit acrilic CH2=C-COOH Axit 2- metylpropenoic; Axit metacrilic CH3 CH3-CH=CH-COOH Axit 2-butenoic; Axit crotonic (dng trans)

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    CH2=CH-CH2-COOH Axit 3-butenoic; Axit vinylaxetic CH2=CH-CH2-CH2-COOH Axit 4-pentenoic; Axit alylaxetic CH3-CC-COOH Axit 2-butinoic; Axit tetrolic CHC-COOH Axit propinoic; Axit propiolic Mt s axit a chc: HOOC-COOH Axit etanioic; Axit oxalic HOOC-CH2-COOH Axit propanoic; Axit malonic HOOC-CH2-CH2-COOH Axit butanioic; Axit sucxinic (Acid succinic) HOOC-(CH2)3-COOH Axit pentanioic; Axit glutaric HOOC-(CH2)4-COOH Axit hexanioic; Axit aipic (Acid adipic) HOOC-(CH2)5-COOH Axit heptanoic; Axit pimelic HOOC-(CH2)6-COOH Axit octanioic; Axit suberic Mt s axit thm: C6H5-COOH ( ) Axit benzoic; Axit benzencacboxilic; Axit phenyl metanoic Axit ptalic; Axit o-ptalic; Axit 1,2-benzenicacboxilic; 1,2-icacboxi benzen Axit isoptalic; Axit 1,3 benzenicacboxilic; m-icacboxibenzen

    COOH

    COOH

    COOH

    C CHOOC COOH

    H HAxit maleic; Axit cis-butenioic

    HOOC

    H

    CC

    COOH

    H

    Axit fumaricAxit trans-butenioic

    COOHCOOH

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    Axit tereptalic; Axit p benzenicacboxilic; 1,4 icacboxibenzen Mt s axit tp chc: CH3-CH-COOH Axit lactic; Axit 2-hiroxipropanoic; Axit -hiroxipropionic OH HOOC-CH2-CH2-CH-COOH Axit glutamic; Axit -aminoglutaric; NH2 Axit 2-aminopentanioic CH2-CH-CH-CH-CH-COOH Axit gluconic; Axit 2,3,4,5,6-hexahiroxihexanoic OH OH OH OH OH OH HOOC-CH2-C-CH2-COOH Axit xitric (Acid citric); Axit limonic; COOH Axit 2-hiroxi-1,2,3-propantricacboxilic Bi tp 100 Vit CTCT ca cc cht sau y: Axit acrilic; Axit axetic; Axit benzoic; Axit fomic; Axit aipic; Axit oxalic; Axit glutamic; Axit metacrilic; Axit lactic; Axit tereptalic; Axit isovaleric; Axit propionic; Axit panmitic; Axit gluconic; Axit malonic. Bi tp 100 Hy cho bit CTCT ca cc cht sau y: Axit stearic; Axit n-butiric; Axit picric; Axit butanoic; Axit lactic; Axit xitric; Axit oleic; Axit propenoic; Axit phenic; Axit - aminoaxetic; Axit enantoic; Axit cloaxetic; Axit limonic (axit xitric, acid citric); Axit metacrilic; Axit 1,3,5 benzentricacboxilic. XII.4. Tnh cht ha hc XII.4.1. Phn ng chy

    CxHy(COOH)n + (x + 4

    ny + )O2 0t (x+n)CO2 + (

    2ny + )H2O

    Axit hu c

    COOH

    COOH

    H

    HC C

    COOH

    Axit xinamicAxit trans-3-phenylpropenoic

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    CxHy-COOH + (x + 4

    1+y )O2 0t (x + 1)CO2 + (

    21+y )H2O

    Axit hu c n chc

    CnH2n + 1COOH + (2

    13 +n ) O2 0t (n + 1)CO2 + (n +1)H2O

    (Cn + 1H2n + 2O2) Axit hu c n chc no mch h Axit ankanoic Ch : Axit hu c n chc no mch h c CTPT dng CnH2nO2 (cng dng vi este n chc no mch h) nn axit hu c no m khi t chy to s mol H2O bng s mol CO2 th l axit hu c n chc no mch h. Cc axit hu c a chc hay c vng khi t chy u to s mol H2O < s mol CO2. (Tng t, este no khi chy to s mol H2O bng s mol CO2 th l este n chc no mch h, cc este khc khi chy u to s mol H2O < s mol CO2) XII.4.2. Axit hu c c y cc tnh cht nh mt axit v c yu Nhm chc axit hu c, COOH, nhm cacboxyl, coi nh tp hp gm hai nhm: nhm OH (nhm hiroxyl) v nhm CO (nhm cacbonyl). Lin kt gia O v H trong nhm hiroxyl t n b phn cc. i in t gp chung gia O vi H b ko v pha O c m in (3,5) ln hn so vi H (2,1). K bn nhm hiroxyl c nhm cacbonyl (CO) rt in t nn cng lm tng thm s phn cc ca lin kt gia O vi H, cng lm cho i in t gp chung gia O vi H cng b ko v pha O. iu ny lm cho H trong nhm cacboxyl rt linh ng (tc H cng mang nhiu in tch dng, d b tch ra di dng ion H+). Do khi ha tan axit hu c vo dung mi nc (H2O), vi s h tr ca dung mi nc rt phn cc, s hirat-ha, th c s phn ly mt phn to ion H+ v ion m gc axit hu c trong dung dch. Tuy nhin s phn ly ion ny khng nhiu, nn axit hu c c y cc tnh cht nh mt axit v c (phn ly to ion H+) v axit hu c l axit yu (khng phn ly hon ton m ch phn ly mt phn to ion, cn a s dng phn t khng phn ly). C th axit hu c c v chua, dung dch axit hu c dn in c, axit hu c lm i mu qu xanh ha , pH dung dch axit < 7. Nguyn nhn ca cc tnh cht ny l do axit hu c c phn ly ion to H+ trong dung dch. Th d: H-COOH dd H-COO + H+ Axit fomic Ion fomiat Ion hiro

    C O

    O

    H2,13,5

    3,5

    2,5

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    CH3-COOH dd CH3-COO + H+ Axit axetic Ion axetat Ion hiro Axit hu c tc dng vi baz to mui v nc

    RCOOH + OH RCOO + H2O Axit hu c Baz Mui ca axit hu c Nc Axit cacboxilic Mui cacboxilat

    Th d: CH3COOH + NaOH CH3COONa + H2O Axit axetic Xt Natri axetat Nc 2HCOOH + Ba(OH)2 Ba(HCOO)2 + 2H2O Axit fomic Bari hiroxit Bari fomiat Nc CH2=CH-COOH + KOH CH2=CH-COOK + H2O Axit acrilic Kali hiroxit Kali acrilat Axit hu c tc dng oxit baz to mui v nc

    2nR-COOH + M2On 2M(R-COO)n + nH2O Axit hu c Oxit baz Mui axit hu c ca KL M

    Th d: 2CH3COOH + Na2O 2CH3COONa + H2O Axit axetic Natri oxit Natri axetat HOOC-COOH + CaO CaC2O4 + H2O Axit oxalic Canxi oxit Canxi oxalat Nc 2C6H5-COOH + K2O 2C6H5-COOK + H2O Axit benzoic Kali oxit Kali benzoat Axit hu c tc dng kim loi (ng trc H trong DT kim loi) to mui v

    kh hiro K Ca Na Mg Al Mn Zn Cr Fe Ni Sn Pb H Cu Ag Hg Pt Au

    nR-COOH + M M(R-COO)n + 2n H2

    Axit hu c Kim loi (ng trc H) Mui axit hu c ca KL M (ha tr n) Th d: 2CH3COOH + Fe Fe(CH3COO)2 + H2 Axit axetic St St (II) axetat Hiro

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    3H-COOH + Al Al(H-COO)3 + 23 H2

    Axit fomic Nhm Nhm fomiat Hiro CH3-COOH + Cu CH2=C-COOH + Na CH2=C-COONa + 1/2H2 CH3 CH3 Axit metacrilic Natri Natri metacrilat Hiro HOOC-CH2-COOH + 2K KOOC-CH2-COOK + H2 Axit malonic Kali Kali malonat Hiro CH3CH2COOH + Hg Axit propionic Thy ngn Ch : Trong cc loi hp cht hu c, ch c axit hu c mi tc dng c cc kim

    loi (khc kim loi kim, v ng trc H trong dy th in ha, nh Mg, Al, Zn, Fe,) to kh hiro thot ra (v mui). (Ru, phenol ch tc dng c kim loi kim).

    Axit hu c tc dng c mui ca axit yu hn to axit mi, mui mi Axit hu c tuy l mt axit yu, nhng n cn mnh hn cc axit rt yu khc nh axit cacbonic (H2CO3), phenol (C6H5-OH), Nn axit hu c y c kh cacbonic (CO2) ra khi mui cacbonat, y c phenol ra khi mui phenolat, 2R-COOH + CO32 2R-COO + CO2 + H2O Axit hu c Mui cacbonat Mui cacboxilat Kh cacbonic Nc R-COOH + C6H5-O R-COO + C6H5-OH Axit hu c Mui phenolat Mui cacboxilat Phenol Th d: 2CH3COOH + CaCO3 Ca(C...