飽和一元酸嘧霉胺鹽燃燒熱測(cè)定及其標(biāo)準(zhǔn)摩爾生成焓和反應(yīng)焓

王美涵, 陳 昀

(沈陽(yáng)大學(xué) 機(jī)械工程學(xué)院, 遼寧 沈陽(yáng) 110044)

飽和一元酸嘧霉胺鹽燃燒熱測(cè)定及其標(biāo)準(zhǔn)摩爾生成焓和反應(yīng)焓

王美涵, 陳 昀

(沈陽(yáng)大學(xué) 機(jī)械工程學(xué)院, 遼寧 沈陽(yáng) 110044)

采用精密氧彈熱量計(jì)測(cè)定了三種脂肪族飽和一元酸嘧霉胺鹽(葵酸嘧霉胺鹽、月桂酸嘧霉胺鹽和肉豆蔻酸嘧霉胺鹽)的恒容燃燒熱cUm分別為(-12 172.6±4.8),(-13 669.9±7.1)和(-15 187.3±6.5) kJ·mol-1.依據(jù)恒容燃燒熱測(cè)定結(jié)果計(jì)算了三種嘧霉胺鹽的標(biāo)準(zhǔn)摩爾燃燒焓c和標(biāo)準(zhǔn)摩爾生成焓f.三種嘧霉胺鹽的標(biāo)準(zhǔn)摩爾生成焓f分別為(-1 186.5±5.6),(-1 045.5±7.8)和(-884.3±7.4) kJ·mol-1,該結(jié)果表明嘧霉胺鹽表現(xiàn)出比嘧霉胺更好的結(jié)構(gòu)穩(wěn)定性.脂肪族飽和一元酸的碳鏈越短,與嘧霉胺反應(yīng)所生成的鹽越穩(wěn)定.結(jié)合嘧霉胺和有機(jī)酸的標(biāo)準(zhǔn)摩爾生成焓,計(jì)算了三種成鹽反應(yīng)焓r分別為(-671.3±5.8),(-469.4±7.9)和(-249.3±7.6) kJ·mol-1,反應(yīng)焓數(shù)據(jù)表明成鹽反應(yīng)為放熱反應(yīng),適當(dāng)降低合成溫度有利于反應(yīng)進(jìn)行.上述結(jié)果為新型嘧霉胺鹽的合成和應(yīng)用提供了熱力學(xué)理論基礎(chǔ).

嘧霉胺鹽; 氧彈熱量計(jì); 燃燒熱; 生成焓; 反應(yīng)焓

嘧霉胺(C12H13N3)屬于苯胺基嘧啶類(lèi)殺菌劑,通過(guò)抑制病菌侵染酶的分泌來(lái)阻止病菌,并殺死病菌.但由于嘧霉胺的飽和蒸氣壓(2.2×10-3Pa,25 ℃)較高,易揮發(fā),減小了其對(duì)病菌作用的持久性,在一定程度上降低了它的藥效.研究表明,可以利用有機(jī)農(nóng)藥的結(jié)構(gòu)特性,讓其與酸或堿成鹽來(lái)改變?cè)械睦砘再|(zhì),并仍然保持良好的生物活性.如,殺蟲(chóng)殺螨劑殺蟲(chóng)脒又稱氯苯脒鹽酸鹽就是通過(guò)不溶于水的克死螨與鹽酸成鹽后成為易溶于水的新型廣譜有機(jī)含氮農(nóng)藥,稻田除草劑苯黃隆也不易溶于水易溶于有機(jī)溶劑,與堿反應(yīng)成鹽后也表現(xiàn)出更優(yōu)良的理化性質(zhì).同樣,嘧霉胺的結(jié)構(gòu)中也有可接受質(zhì)子的-NH-基,文獻(xiàn)報(bào)道[1]嘧霉胺與酸結(jié)合成鹽后,不僅可以降低飽和蒸氣壓,而且還能提高抑制、殺滅植物病菌的性能.因此,嘧霉胺鹽成為一類(lèi)非常重要的含氮生物活性物質(zhì),在農(nóng)藥和醫(yī)藥等領(lǐng)域應(yīng)用前景廣泛.迄今為止,有關(guān)嘧霉胺鹽熱力學(xué)性質(zhì)和化學(xué)穩(wěn)定性的研究還未廣泛開(kāi)展,雖然已有葵酸嘧霉胺鹽[2]、月桂酸嘧霉胺鹽[3]和肉豆蔻酸嘧霉胺鹽[4]的低溫?zé)崛莺蜔岱€(wěn)定性報(bào)道,但未見(jiàn)三種飽和一元酸嘧霉胺鹽標(biāo)準(zhǔn)摩爾生成焓和成鹽反應(yīng)焓的報(bào)道.標(biāo)準(zhǔn)摩爾生成焓和成鹽反應(yīng)焓的測(cè)定對(duì)研究嘧霉胺鹽的性能,開(kāi)發(fā)和利用嘧霉胺鹽,及深入研究其成鹽反應(yīng)過(guò)程均具有重要現(xiàn)實(shí)意義.為了進(jìn)一步拓展嘧霉胺鹽的實(shí)際應(yīng)用,迫切需要其標(biāo)準(zhǔn)摩爾燃燒焓、標(biāo)準(zhǔn)摩爾生成焓和成鹽反應(yīng)焓數(shù)據(jù).為此,本文選用葵酸(C10H20O2)、月桂酸(C12H24O2)和肉豆蔻酸(C14H28O2)三種飽和有機(jī)一元酸與嘧霉胺反應(yīng)生成嘧霉胺鹽,測(cè)定了三種嘧霉胺鹽的恒容燃燒熱,計(jì)算出它們的標(biāo)準(zhǔn)摩爾燃燒焓、標(biāo)準(zhǔn)摩爾生成焓以及成鹽反應(yīng)焓.從熱力學(xué)的角度分析和判斷了嘧霉胺鹽的穩(wěn)定性以及成鹽反應(yīng)的熱效應(yīng),為新型嘧霉胺鹽的合成與應(yīng)用提供了必要的基礎(chǔ)數(shù)據(jù).

1 實(shí)驗(yàn)部分

1.1 飽和一元酸嘧霉胺鹽的合成與表征

攪拌下,在含有0.01 mol/L有機(jī)酸的無(wú)水乙醇溶液中滴加含有0.01 mol/L嘧霉胺的無(wú)水乙醇溶液,室溫下反應(yīng)60 min.靜置析出固體產(chǎn)物,抽濾,無(wú)水乙醇重結(jié)晶3次,得到產(chǎn)物嘧霉胺鹽.反應(yīng)方程式如下:

采用傅立葉變換紅外光譜儀(FTIR model: Alpha Centauri IR-400)、核磁共振譜儀(1HNMR model: Varian unity INOVA-400)和元素分析儀(PE-2400)確定了(a)葵酸嘧霉胺鹽(C22H33N3O2)、(b)月桂酸嘧霉胺鹽(C24H37N3O2)和(c)肉豆蔻酸嘧霉胺鹽(C26H41N3O2)的結(jié)構(gòu)和組成.

1.2 飽和一元酸嘧霉胺鹽燃燒熱的測(cè)定

燃燒熱測(cè)量在中國(guó)科學(xué)院大連化學(xué)物理研究所材料熱化學(xué)創(chuàng)新課題組的精密靜止氧彈燃燒量熱計(jì)上進(jìn)行,該熱量計(jì)的構(gòu)造與測(cè)量原理可參見(jiàn)文獻(xiàn)[5].

熱量計(jì)能當(dāng)量通過(guò)測(cè)定10次NIST 39苯甲酸的燃燒實(shí)驗(yàn)來(lái)確定,每次苯甲酸用量約為0.7 g,擠壓成片,氧彈內(nèi)氧氣壓力為3.01 MPa,內(nèi)裝有0.001 dm3蒸餾水,實(shí)驗(yàn)所用氧氣純度為99.998%.在實(shí)驗(yàn)條件下苯甲酸燃燒熱c=-(26 434±3) J·g-1,熱量計(jì)能當(dāng)量εcalor=(13 572.22±0.98) J·K-1.

三種嘧霉胺鹽的恒容燃燒熱的測(cè)定可按下式計(jì)算:

式中:ζcalor是氧彈燃燒量熱量計(jì)能當(dāng)量;ΔT為校正后的溫升,K;M為樣品的摩爾質(zhì)量,g·mol-1;W為樣品質(zhì)量,g.鎳絲燃燒產(chǎn)生的熱量QNi=2.929ΔL,J.其中ΔL為燃燒消耗的鎳絲長(zhǎng)度,cm.高純氧氣中的微量N2雜質(zhì)和含氮化合物中N元素燃燒生成硝酸的能量QHNO3=59.8N·V, J.其中:N是NaOH溶液的濃度,mol·L-1;V為消耗NaOH溶液的體積,cm3.每種嘧霉胺鹽的燃燒熱重復(fù)測(cè)定6次.

2 結(jié)果與討論

2.1 飽和一元酸嘧霉胺鹽的恒容燃燒熱

三種飽和一元酸嘧霉胺鹽的恒容燃燒熱測(cè)定結(jié)果列入表1.葵酸嘧霉胺鹽、月桂酸嘧霉胺鹽和肉豆蔻酸嘧霉胺鹽的恒容燃燒熱cUm實(shí)驗(yàn)測(cè)定平均值分別為(-12 172.6±4.8)、(-13 669.9±7.1)和(-15 187.3±6.5) kJ·mol-1.

2.2 飽和一元酸嘧霉胺鹽的標(biāo)準(zhǔn)摩爾燃燒焓

葵酸嘧霉胺鹽(C22H33N3O2)、月桂酸嘧霉胺鹽(C24H37N3O2)和肉豆蔻酸嘧霉胺鹽(C26H41N3O2)的燃燒反應(yīng)方程式如下:

則它們的標(biāo)準(zhǔn)摩爾燃燒焓可從下式計(jì)算得到:

其中,

按照式(3)計(jì)算出三種飽和一元酸嘧霉胺鹽的標(biāo)準(zhǔn)摩爾燃燒焓c,結(jié)果列于表2中.

表1. 一元酸嘧霉胺鹽的恒容燃燒熱實(shí)驗(yàn)結(jié)果Table 1 The values of the combustion energies of the pyrimethanil salts

表2一元酸嘧霉胺鹽的標(biāo)準(zhǔn)摩爾燃燒焓和標(biāo)準(zhǔn)摩爾生成焓

Table 2 The values of standard molar combustion enthalpy and standard molar formation enthalpy of the pyrimethanil salts

樣 品標(biāo)準(zhǔn)摩爾燃燒焓ΔcHom/(kJ·mol-1)標(biāo)準(zhǔn)摩爾生成焓ΔfHom/(kJ·mol-1)葵酸嘧霉胺鹽(C22H33N3O2)-12186.9±4.8-1186.5±5.6月桂酸嘧霉胺鹽(C24H37N3O2)-13686.6±7.1-1045.5±7.8肉豆蔻酸嘧霉胺鹽(C26H41N3O2)-15206.5±6.5-884.3±7.4

2.3 飽和一元酸嘧霉胺鹽的標(biāo)準(zhǔn)摩爾生成焓

根據(jù)Hess定律,從化合物的燃燒反應(yīng)方程式,可得其標(biāo)準(zhǔn)摩爾生成焓.葵酸嘧霉胺鹽、月桂酸嘧霉胺鹽和肉豆蔻酸嘧霉胺鹽的熱化學(xué)循環(huán)方程式為

進(jìn)而得到

2.4 飽和一元酸嘧霉胺鹽的成鹽反應(yīng)焓

反應(yīng)物嘧霉胺的標(biāo)準(zhǔn)摩爾生成焓參考文獻(xiàn)值[7]f(嘧霉胺)=(198.5±1.5) kJ·mol-1.反應(yīng)物葵酸、月桂酸和肉豆蔻酸的標(biāo)準(zhǔn)摩爾生成焓數(shù)據(jù)來(lái)自DIPPR物性數(shù)據(jù)庫(kù)[8],分別為-713.70,-774.58和-833.49 kJ·mol-1.從反應(yīng)物和產(chǎn)物的標(biāo)準(zhǔn)摩爾生成焓數(shù)據(jù),按照下式計(jì)算得到溫度T=298.15 K、壓強(qiáng)p=100 kPa下三種嘧霉胺鹽的成鹽反應(yīng)焓,結(jié)果列于表3中.

表3 一元酸嘧霉胺鹽的成鹽反應(yīng)焓

反應(yīng)焓數(shù)據(jù)對(duì)合成反應(yīng)溫度的控制至關(guān)重要.從反應(yīng)焓數(shù)據(jù)可以看出嘧霉胺與飽和一元酸的成鹽反應(yīng)均為放熱反應(yīng),因此反應(yīng)在室溫條件下即可發(fā)生,若在反應(yīng)過(guò)程中及時(shí)將熱量導(dǎo)出,更加有利于反應(yīng)的進(jìn)行.

3 結(jié) 論

采用精密氧彈熱量計(jì)測(cè)定了葵酸嘧霉胺鹽、月桂酸嘧霉胺鹽、肉豆蔻酸嘧霉胺鹽在298.15 K的恒容燃燒熱cUm.根據(jù)熱化學(xué)方程式和蓋斯定律,由恒容燃燒焓計(jì)算出它們的標(biāo)準(zhǔn)摩爾生成焓f分別為(-1 186.5±5.6),(-1 045.5±7.8)和(-884.3±7.4) kJ·mol-1.標(biāo)準(zhǔn)摩爾生成焓結(jié)果表明,嘧霉胺鹽比嘧霉胺結(jié)構(gòu)更穩(wěn)定,能量更低.隨著脂肪族飽和一元酸碳鏈的增加,嘧霉胺鹽的穩(wěn)定性減弱.由反應(yīng)物和生成物的標(biāo)準(zhǔn)摩爾生成焓計(jì)算得到三種嘧霉胺鹽成鹽反應(yīng)焓r分別為(-671.3±5.8),(-469.4±7.9)和(-249.3±7.6) kJ·mol-1.反應(yīng)焓數(shù)據(jù)表明嘧霉胺與飽和一元酸的成鹽反應(yīng)均為放熱反應(yīng),因此反應(yīng)在室溫條件下即可進(jìn)行.

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【責(zé)任編輯:胡天慧】

DeterminationofCombustionHeat,StandardFormationEnthalpyandReactionEnthalpyofPyrimethanilSalts

WangMeihan,ChenYun

(School of Mechanical and Engineering, Shenyang University, Shenyang 110044, China)

The constant volume combustion heatcUmof pyrimethanil capric salt, pyrimethanil lauric salt and pyrimethanil myristic salt was measured to be (-12 172.6±4.8), (-13 669.9±7.1) and (-15 187.3±6.5) kJ·mol-1, respectively, using oxygen-bomb combustion calorimetry at 298.15 K. The standard mole combustion enthalpycand the standard mole formation enthalpyfwere calculated based on the value ofc. The standard mole formation enthalpyfof three pyrimethanil salts was determined to be (-1 186.5±5.6), (-1 045.5±7.8) and (-884.3±7.4) kJ·mol-1, respectively. The data suggest that shorter carbon chain of aliphatic monocarboxylic acid, the more chemical stable of pyrimethanil salt. The reaction heatrof three pyrimethanil salts was calculated to be (-671.3±5.8), (-469.4±7.9) and (-249.3±7.6) kJ·mol-1, respectively, which indicates reactions heat between pyrimethanil and three organic acids are exothermic. So the reaction could take place at room temperature and decreasing temperature is favorable for the reaction. The above results offer the theoretical basis for the synthesis and application of novel pyrimethanil salts.

pyrimethanil salts; oxygen-bomb combustion calorimetry; heat of combustion; formation enthalpy; reaction enthalpy

O 642.3

A

2017-09-15

遼寧省優(yōu)秀人才支持計(jì)劃(LJQ2014132).

王美涵(1977-),女,遼寧沈陽(yáng)人,沈陽(yáng)大學(xué)教授,博士.

2095-5456(2017)06-0448-04