Khi ph Trang 1

M U

Phng php khi ph hay ph khi lng vit tt l MS (Mass Spectrometry), l mt phng php phn tch cng c quan trng phn tch thnh phn v cu trc ca cc hp cht v c v hu c. Lch s pht trin ca phng php c bt u t th k XX. Thompson l ngi s dng my ph khi lng trong phn tch ha hc, xc nh khi lng nguyn t v phn t. Conrad (1930) a thng bo u tin v nghin cu ph khi lng ca cc hp cht hu c. Tip theo l s pht trin nhanh chng trong lnh vc ny.

Nm 1940, ph khi c s dng vo vic pht hin du m v nhng nm 1950 c s dng phn tch cc mu hoocmon va stesoit. S kt hp sc k khi ph (GC/MS) c thc hin vo nhng nm 1960, cn s kt hp vi sc k lng khi ph (LC/MS) c tin hnh vo nhng nm 1970. ng thi pht trin nhanh chng trong nhiu k thut mi ca phng php ph khi lng nh phng php b bom nguyn t (FAB), phng php phun nhit (TS), khi ph k t cc, khi ph k thi gian bay (TOF), Phm vi ng dng ca phng php ph khi lng rt rng ln, c bit c ngha quan trng i vi ngnh ha hc hu c, ha sinh v ngnh ha hc v c, nguyn t ng v. V vy, cc sch v ti liu v phng php ph khi lng thng c phn thnh hai loi: Ph khi lng cc hp cht v c v ha sinh v Ph khi lng ca cc nguyn t v hp cht v c.

Khi ph Trang 2

KHI PH

I. C S L THUYT CA PHNG PHP KHI PH 1. Nguyn tc chung

Khi ph l mt phng php nghin cu cc cht bng cch o chnh xc khi lng phn t ca cht da trn in tch ion. Thit b chuyn dng l khi ph k. Cht nghin cu trc tin c chuyn thnh trng thi hi, sau c a vo nghin cu trong b phn phn tch ca my khi ph k.

Ngi ta c th dng phng php khi ph nghin cu tt c cc nguyn t hay hp cht c th bin thnh dng kh hay hi.

i vi cc hp cht v c, phng php phn tch khi ph thng dng nghin cu thnh phn ng v hoc xc nh vt cc cht nghin cu.

i vi cc hp cht hu c, phng php phn tch khi ph thng c dng trong qu trnh ng nht cht hoc phn tch cu trc.

y bi bo co ch gii hn trong phm vi ng dng khi ph phn tch cu trc, t xc nh cng thc phn t ca cc hp cht hu c.2. Qu trnh ion ha v qu trnh phn mnh2.1. Qu trnh ion ha

L qu trnh bn ph cc phn t hp cht hu c trung ha thnh cc ion phn t mang in tch dng bng cc phn t mang nng lng cao:

ABCD + e ABCD + 2e Ion phn tS bn ph ny s lm tch mt in t ra khi phn t kha st lm cho phn t

bin thnh ion dng, c gi l ion phn t. Ion phn t l ion dng v cng l gc t do v n cha s l in t, nn ion phn t cn gi l cation gc hay ion gc.

Qu trnh ion ha c th c thc hin bng nhiu phng php khc nhau: Phng php ion ha bng va chm in t: y l phng php ion ha ph bin

nht. Trong bung ion ha, cc in t pht ra t cathode lm bng vonfram hoc reni, s bay v anode vi vn tc ln. Cc phn t cht nghin cu trng thi hi s va chm vi in t trong bung ion ha, c th nhn nng lng in t v b ion ha.

Phng php ion ha bng trng in t: y cng l mt phng php ion ha c dng kh ph bin. Ti bung ion ha, ngi ta t cc b phn pht ra t trng, l cc mi nhn c bit di dng dy dn mnh (2.5 m) hay cc li mnh. Ngi ta t in cc vo cc mi nhn. ti cc mi nhn s cho mt trng in t c gradien t 107 - 1010 V/cm. Di nh hng ca trng in t mnh ny, cc in t bt khi phn t cht nghin cu do hiu ng ng hm v y khng gy ra s kch thch. Vy trong phng php ion ha ny, cc ion phn t c to thnh vn gi

Khi ph Trang 3

nguyn trng thi c bn, do cc vch ph s rt mnh.Ngoi hai phng php ion ha k trn, ngi ta cn dng cc phng php khc

nh: ion ha ha hc, chiu x bng cc photon, bn ph nguyn t nhanh Tuy nhin, cc phng php ion ha ny t ph bin hn so vi hai phng php va m t trn y.2.2. Qu trnh phn mnh

Vi nng lng bn ph rt cao th ion phn t va to thnh c th bin thnh cc mnh ion dng nh hn, hoc cc ion gc, hoc cc gc t do, hoc cc phn t trung ha nh hn. Qu trnh ny gi l qu trnh phn mnh.

ABCD + e ABC + D

AB + CD

A + BCD

A + BCD

S bn ph ny ph thuc vo cu to cht, phng php bn ph v nng lng bn ph.

Ion phn t v cc ion mnh l cc phn t c khi lng. Nu gi khi lng ca mt ion l m v in tch ca n l e th t s z= m/e c gi l s khi. V s in tch trn mi ion thng bng +1 nn gi tr m/e ca mi ion s n gin l khi lng ca n. Cc mnh ion mang in tch dng s c b phn ghi nhn tn hiu ca my khi ph chuyn thnh nhng mi ph ty theo t l m/e ny.

Ngoi ra trong qu trnh phn mnh cn c s to thnh cc ion m thi gian tn ti ca n rt nh (< 10-5 giy) gi l ion gi bn, k hiu m*. Khi my khng th ghi li s xut hin ca n y c. Tuy nhin, ngi ta c th nh du s xut hin ca n trn ph v ghi nhn c cc ion ban u cng nh cc ion cui.

m* = m2/m0

Vi: m0 l khi lng ca ion ban u m l khi lng ca ion cui 3. Mt s c ch phn mnh in hnh

S phn ha cc hp cht hu c qua s va chm vi electron thng xy ra theo nhng quy lut nht nh, da vo nhng quy lut ngi ta c th gii thch c cu to ca cc hp cht hu c. Cc quy lut ny c gi l c ch phn mnh phn t. Di y xin gii thiu mt s c ch phn mnh in hnh:

Khi ph Trang 4

3.1. C ch tch ankyl (F1)Nhng ankan v nhng hp cht cha nhm ankyl b ph v di s hnh thnh

ca mt ion ankyl v mt gc:

C H

H

HC CH

H

H

H

H

C CH

H

H

H

H

C

H

H

H

Nhng ankyl gn vi cc nhm chc X= OH, SH, OR th s tch nhm chc X cho mt ion dng v mt gc:

C CH

H

H

H

H

X C CH

H

H

H

HX

3.2. C ch tch olefin (F2)Nhng ion ankyl mch di c th tch loi phn t olefin nh sau:

C CH

H

H

H

H

C

H

HCH

H

HC C

H

H

H

H

3.3. C ch tch anlyl (F3)Nhng phn t olefin mch di do b mt i mt electron to thnh mt ion gc

nn c s chuyn dch electron tip theo trong phn t dn n vic tch ra mt gc ankyl v mt ion dng anlyl bn, tn ti di hai dng cng hng (1) v (2):

e C C C CC C C C

C CC CC CC

(1) (2)3.4. C ch tch ion tropyli (F4)

Cc hp cht benzen c nhm th CH2X (X= H, ankyl, OH, SH, -COR,) gn vi vng benzen, thng tch gc X cho ion tropyli theo c ch sau:

CH2 X

XCH2

m/e = 91 Ion tropyli

Khi ph Trang 5

3.5. C ch tch oni (F5) Cc hp cht cha nhm X (X= OH, SH, OR, SR, NH2, NHR, NR2) thng tch

mt vi nhm metyl, etyl,... cho nhm ion kiu oni >C=X+:

C C X C XC C X

3.6. C ch tch Retro-Diels-Alder (F6)Cc hp cht vng cha ni i thng c tch ra cho cc olefin theo phn

ng Retro-Diels-Alder:

R Re

R

3.7. Chuyn v McLafferty (H1) Cc nguyn t hidro v tr i vi cc ni i C=C hoc C=O thng c s

chuyn v n nguyn t cacbon ca ni i ny:a/

CH2CH2 CH2

CH

H CH2 CH2CH2

CH3

CHCH2

b/

CH2CH2 CH2

C

OH

OR

CH2CH2

OH

CORCH2

3.8. Chuyn v gc (H2)

Ion (I) xut hin qua s tch oni F5 ca mt xicloankyl c cha trung tm tch in dng v mt gc. Qua s chuyn v ca nguyn t H trong phn t dn n s tch ra thnh ion dng v mt gc ring:

X

H C

HH

X

H CH

H

X

H

H

HC H

X

Khi ph Trang 6

(I)3.9. Chuyn v ancol (H3)

Cc phn t ancol hay amin d dng tch H2O hay nhm NHR2 qua chuyn v ancol nh sau:

C X

CH

(CH2)nCH

HX

C

C

(CH2)nCH

C XH

C

(CH2)nC

HC XH

C

(CH2)nCH

(X= OH, NR2)3.10. Cng hp Retro (H4)

HXH

X

S tch phn t HX tng t s cng hp 1,4 hnh thnh mt ion dien lin hp v mt phn t bn. V d: s tch phn t metanol t metyl este ca axit salixilic nh sau:

C

O

OCH3OH

OCH3

OH

O

i vi vng thm phn ng cng hp Retro (H4) c th tranh chp vi phn ng tch ion tropyli (F4):

OH OHH2OH4 F4

m/e = 104 m/e = 105(23,6 %) (4 %)

3.11. Chuyn v oni (H5)a. R CH XH CnH2nR CH X (CnH2n+1)

Khi ph Trang 7

b. X CH (CnH2n+1) X CH2 CnH2nDo chuyn v H t gc CnH2n+1 tch ra phn t anken CnH2n. Ion mi c to

ra c cng thc tng v s khi m/e = 31 tng t nh tch oni (F5), v d:

m/e = 31

OH CH2 OH

O

R

R O H5 HO CH2 OH

3.12. Chuyn v ion lng cc (H6)

CXH

(CH2)n

CY

CX

(CH2)n

CHY

Phan ung tiep theo

C ch ny, chuyn v H da trn s tng tc ni phn t ca ion nhm +XH v nhm Y, v d:

DCH

O

(CH2)nCOCH3

ODCH

O

(CH2)nC OCH

OD

(CH2)nCOCH3

O

H6 H3

3.13. Sp xp li phn tS phn ha phn t c th xy ra do s sp xp li phn t v tch ra mt phn

ca phn t nh s sau:A B C A C B

V d: cc dng phn t di y, s phn ha phn t xy ra do tch ra nhm chc X:

X X

X = NH, O, S, N=N, CO, CH2, CH=OHoc lin kt C-C mch nhnh ca vng thm v sp xp li phn t

Khi ph Trang 8

H

CH CH CH CH

H

CH2CH

H

CH2CH2CH

CH3

CH

CH

2

CH3

Cc xeton vng ct nhm C=O v ph v vng cho cc ion mnh nh s sau:

Ar

O

Ar

O

Ar

ArAr

II. K THUT THC NGHIM

Nguyn tc my o khi phNu nh trong cc phng php ph hng ngoi, ph t ngoi, ph cng hng t

ht nhn ngi ta gi nguyn phn t nghin cu th phng php ph khi lng ngi ta li ph hy phn t nghin cu chng. Nh vy, ni mt cch n gin, my ph khi lng c ch to thc hin 3 nhim v c bn l: chuyn cht nghin cu thnh th kh (lm bay hi mu nghin cu p sut thp v nhit thch hp); to ra cc ion t cc phn t kh ; phn tch cc ion ri ghi li tn hiu theo t s khi lng/in tch (m/ze) ca chng. Bi v xc xut to thnh cc ion c z >1 l rt nh v v e = const (e l in tch ca mt electron) do thng thng m/ze chnh l khi lng ca ion. Nh th my ph khi lng l mt thit b sn xut ra cc ion v xc nh khi lng ca chng (phn tch cc ion)

Khi ph Trang 9

V mt nguyn l hot ng, c th s ha mt my ph khi lng thnh 4 khi:

Tt nhin l my ph khi lng phi c ni vi my tnh t ng ha, tng hiu qu s dng v khai thc cc kt qu thu c.

khi lm bay hi, mu c th c t nng ti 200 3000C p sut thp, do c th lm bay hi c nhng cht c khi lng phn t ln ti 1000 nu n khng cha cc nhm phn cc, hoc c khi lng phn t ti 300 nu l nhng phn t phn cc va phi. Khi lng mu ch cn vi microgram.

Khi to ra cc ion c gi l bung ion ha. Mu sau khi ha hi c phng vo bung ion ha qua khe a v b bn ph bi chm electron b (hnh 2.1.1). Do kt qu va p phn t cht nghin cu vi cc electron c nng lng cao (~ 70 eV) s to ra cc ion dng chuyn ng hng v cc bn gia tc c v d. Nhng ion m th b ht v pha thnh sau ca bung ion ha (v tch in dng so vi pha trc ca bung ion ha). Nhng ion dng i qua cc bn c v d c gia tc di tc dng ca hiu in th V (khong 8 kV) ri ri khi bung ion ha t khe g (hnh 2.1.1). Trong trng hp c bit, mu c th c a thng vo bung ion ha khng qua khi lm bay hi. Khi ch cn vi ng thm ch pg (10-9 10-12g).

Khi to ra cc ion

Khi phn tch cc ion

Khi thu nhn tn hiu cc ion, khuch i ri

ghi thnh ph

Khi lm bay hi mu

Hi Ti khi phn tcha b c d g

Khi ph Trang 10

Hnh 2.1.1 S bung ion haVic phn tch cc ion c thc hin hai khi: khi phn tch ion, khi ghi

nhn tn hiu v ghi ph.Khi phn tch ion c nhim v phn tch chm ion (gm ion phn t v rt nhiu

cc ion mnh khc nhau) sao cho b phn tip theo c th thu nhn c tn hiu ca tng loi ion ghi li thnh ph. m bo chuyn ng t do cho cc ion, bung ion ha cng nh khi phn tch ngi ta phi ht chn khng ti ~ 10-7 mmHg (thng thng ti 10-6 mmHg). C nhiu cch phn tch chm ion da vo cc nh lut vt l khc nhau, di y s gii thiu cch phn tch bng t. b phn

tch bng t,

ion sau khi ra khi khe g (hnh

2.1.2) chu tc dng ca mt

t trng H. Di nh hng ca t trng cc ion chuyn ng theo mt qu o trn. Bn knh r ca qu o trn ph thuc vo cc tham s sau: 1) hiu in th V gia hai bn gia tc c v d (hnh 2.1.1); 2) khi lng m ca ion; 3) in tch z ca ion; 4) cng ca t trng H.Mi lin h gia cc i lng c biu hin bi cng thc: (2.1.3)

i vi mt ion t s m/z l c nh, do bng cch thay i cng t trng H ta s thay i c bn knh r ca qu o chuyn ng ca n. Ni mt cch khc ta c th lm cho cc ion c m/z khc nhau ln lt i qua khe h

VrH

zm

2

22

=

H

2r

ihg

Hnh 2.1.2 S phn tch ion bng t trngg- khe thng vi bung ion ha; h- khe thu nhn; i- bn thu nhn

Khi ph Trang 11

ti bn thu nhn I (hnh 2.1.2). Vi cch phn tch ny ngi ta d dng phn bit c cc ion vi khi lng khc nhau 1 n v C. Ni mt cch khc, trn ph khi lng ca cc ion u c lm trn.

Khi thu nhn tn hiu v ghi ph: thu nhn v khuch i tn hiu ca cc ion ngi ta dng nhng thit b khc nhau ph hp vi cc cch phn tch ion s dng b phn phn tch. Cc thng tin c a vo my tnh. b nh ca my tnh c cha sn ph ca hng lot hp cht hu c c chn lc. Khi ph ca mt hp cht nghin cu va c ghi xong, my tnh t ng so snh vi cc ph trong b nh nhn bit hp cht nghin cu. Ph phn gii thp c s ha c th c lu tr trong my tnh li c th c khi phc di dng biu v c in ra mt cch t ng. phng php ph khi lng phn gii cao, cc thng tin c x l mt my tnh c chng trnh ha vi khi lng chnh xc ca C, H, O, N...T khi lng chnh xc ca cc ion, my tnh s cho bit thnh phn ca chng. Thnh phn ca cc ion c t ng ghi ra theo chiu tng gi tr m/z v c sp xp theo tng loi (v d loi ion cha C, H, loi ion cha C, H, O...). Ngi ta gi l bn nguyn t. Ngy nay ngi ta ang tip tc ci tin my ph v s dng my tnh tr gip cho vic gii ph.III. PH KHI LNG CA MT S CHT3.1. Ph khi ca Hidrocacbon3.1.1. Hidrocacbon bo ha

Ion phn t ca hidrocacbon bo ha lun xut hin nhng yu vi cc hidrocacbon mch di. nh gi bn ion phn t ngi ta a ra bn ion phn t WM c tnh nh sau:

%1001 = IWM y WM l cng ion phn t; I l tng cng ca cc ion xut hin

trn ph. bn ion phn t ph thuc vo cu to phn t:Ion phn t ca hidrocacbon vng bo ha bn hn mch thng bo ha.Ion phn t ca hidrocacbon thm bn hn ca hidrocacbon bo ha v cha bo ha.

Hidrocacbon WMHexan

Hexen-1Xiclohexan

Xiclohexadien-1,3ivinylaxetilen

2,84,6

15,516,523,2

Khi ph Trang 12

Benzen 33,2 bn ion phn t ca hidrocacbon

Cc ankan mch nhnh c khuynh hng ct cc nhm th mch nhnh trc tin nh ph khi sau:

Trn ph cho thy C3H7+ vi m/e = 57 c cng ln nht do ct mch nhnh ca phn t hidrocacbon.

Hp cht vng bo ha ni chung bn vng hn cc ankan mch thng qua va chm electron. Ion phn t xut hin c cng ln hn 3 ln so vi cc pic tng ng.

Hnh 3.1.1. Ph khi ca hexan

3.1.2. AnkenNi chung ion phn t ca anken trong ph khi u xut hin vi cng

mnh. S khi thng gp l 27, 41, 55,...

CH3 CH2 CH2 CH CH343 43

2-metylpentan

CH3 CH CH CH343 43

3-metylpentan

CH3 CH2 CH CH2 CH329 57

2,3-dimetylpentan

Hexan (C6H

14) MW = 86.18

CH CH2 CH2 RCHR+ F3 R CH CH CH2

R CH CH CH2CH2 R++

+

Khi ph Trang 13

Hnh 3.1.2.1. Ph khi ca trans hex-3-en

Hnh 3.1.2.2. Ph khi ca trans hex-2-enS ph v phn t ca trans hex-2-en theo s sau:

Khi ph Trang 14

H3C C CH

CH2CH2CH3H

H3C C CH

CH2CH2H+

H3C C CH

CH2H+ CH3 CH CH2

+

M+ 84

m/e = 69 m/e = 55 m/e = 42i vi cc olefin c s cacbon C6 n C9 xy ra qu trnh ion ha theo qui lut sau:

Cc anken c ni i u mch (R= H) thng ion ha theo c ch F1 cho ion c s khi m/e 42, 56, 70.

Ch c nhm metyl tch theo c ch F3, to ra s ng phn ha. Cc anken c s khi trung bnh thng cho ion m/e 55 vi cng mnh. Cc ion m/e 43, 57 c cng mnh vi cc mch nhnh v tr 4.

3.1.3. AnkinAnkin cho ion phn t t rt yu n vng mt, cc ion thng xut hin c s

khi m/e 39, 53, 67,...Ankylaxetilen trong ph khi b ph v phn t lin kt -C-C=C nh sau:

C ch chuyn v Mclafferty cng thng xy ra trong qu trnh ion ha phn t cho m/e = 40:

CH C CH2 R CH C CH2

CH C CH2++

+ R

H R

R CH CH2 CH2 C CH2+

+

+

m/e = 40

Khi ph Trang 15

Hnh 3.1.3. Ph khi ca pent-1-in3.1.4. Ankylbenzen

Ni chung ankylbenzen cho ion phn t mnh v cc ion mnh thng gp l m/e 39, 50, 51, 52, 65, 77, 91, 105, 119,...

Qu trnh ph v phn t xy ra theo c ch ct ion tropyli:+

CH2 R CH2+

R+

m/e 91 (ion tropyli)

C ch chuyn v Mclafferty cng thng xut hin trong qu trnh ion ha phn t ankylbenzen c gc ankyl mch di:

RH

m/e = 92

+ +

Khi ph Trang 16

Hnh 3.1.4. Ph khi ca toluen

3.1.5. H vng thm ngng tPh khi ca cc vng thm ngng t nh naphtalen, phenantren, tetraxen, pyren

cho ion phn t M v (M 1) cn rt t xy ra s ph v phn t khc nh ph khi ca naphtalen cho ion phn t M 128 (100%) cn cc ion khc c cng ion nh hn 10%.

CH CH+

+

+

_

m/e 102

m/e 51m/e 64m/e 75

C4H3

++ +

+H2C OH

Khi ph Trang 17

Hnh 3.1.5. Ph khi ca naphtalen

3.2. Ph khi ca ancolAncol cho ion phn t yu hoc vng mt v cc ion mnh m/e 31, 45, 59, ...(M

18).

3.2.1. Ancol bc 1Ancol bc 1 ion ha ph v phn t thun li theo c ch tch oxoni F5 v tch

ankyl F1:

ROH

m/e 31F5 H3

_ H2O(M - 18)

++

(M - 17)

F1

Theo c ch F5 phn t ancol bc 1 lun tch (m/e 31), theo c ch tch ankyl F1 tch ra ion dng R+ v gc OH v theo c ch chuyn v cho mt phn t trung ha v H2O.

Hnh 3.2.1. Ph khi ca pentan-3-ol

3.2.2. Ancol bc 2Ancol bc 2 cng cho cc qu trnh ion ha ct phn t theo c ch tch oxoni

F5, ct ankyl F1 v chuyn v tch loi H2O cho phn t trung ha theo s sau:

3-Pentanol (C5H

12O) MW = 88.15

Khi ph Trang 18

+R CH OH

R'

(M - 18)+

F5 F1(M - 17)

H3_ H2O

Ni chung ancol bc 2 cng cho ion 31, 45, 59 nh ancol bc 1.

Hnh 3.2.2. Ph khi ca propan-2-ol3.2.3. Ancol bc 3

Ion ha phn t theo c ch F1 ct nhm OH v c ch F5 ct gc ankyl:

+R1 C

R

OH

R2

F1

CH3 CH2 C

OH

CH3

CH3

59

H3C CH CH3OH

45

H3C CH CH2

OH OH

45 31

61

Khi ph Trang 19

Hnh 3.2.3. Ph khi ca 2-metylbutan-2-ol3.2.4. Poliol

Ph khi ca poliol ch ra s ct t nguyn t H hay nhm R trong qu trnh ion ha v ct lin kt -C-C i vi nguyn t oxi nh sau:

CH CH2 OH

HO

R

HO CH CH2 OH

CH2 OH R CH OH

+

++

++

R

m/e 31

Hnh 3.2.4. Ph khi ca propan-1,2-iol3.2.5. Ancol thm

Khi ph Trang 20

Ph khi ca ancol thm u cho ion phn t v ion (M-OH)+, ring ancol o-metyl benzylic cho ion (M-H2O)+ vi cng mnh.

Hnh 3.2.5. Ph khi ca benzylancol

3.3. Ph khi ca ete3.3.1. Ete mch thng

Ete mch thng cho ion phn t vi cng yu, cc s khi thng xut hin trn ph l 31, 45, 59, 73... do s xut hin cc ion mnh RO+ v ROCH2+ bi ct lin kt C-O hay lin kt ca phn t.V d:

H3C CH2 CH

CH3

O CH2 CH3

H3C CH O CH2 CH2 H

H3C CH2 CH O CH2 CH3

CH3 CH OH

CH3 CH2

CH3 CH2 O CH3 CH OH

+

+

+

+

+

+m/e 73 m/e 45

m/e 87 m/e 29

m/e 45 m/e 45 (100%)

R C O

Khi ph Trang 21

Hnh 3.3.1. Ph khi ca etyl metyl ete

3.3.2. Ete thmEte thm cho ion phn t mnh v u tin ph v lin kt C-O cho ion aryl.

Hnh 3.3.2. Ph khi ca metyl phenyl ete

3.4. Ph khi ca andehid v xeton3.4.1. Andehid

Cc andehid cho ion phn t vi cng yu v cc khi lng m/e (M-18), (M-28), (M-44), v 44, 58, 72.

C ch ion ha chnh l chuyn v McLafferty H1, c ch tch ioni F5 ch xy ra vi cc andehid u dy. Khi R C2H5 th s chuyn v H1 c th xy ra theo hai hng:

Ethyl methyl ether (C3H

8O) MW = 60.10

4-Heptanon (C7H

14O) MW = 114.19

Khi ph Trang 22

OR

R'

R'OH

R

+

+

+F

m/e (43 + R)

m/e (27 + R)

Trn ph ca andehid cng xut hin ion (M-18) do tch nc, (M-28) do tch CO hay C2H4 nhng c ch ion ha cha gii thch c.Cc andehid mch thng thng to ion (M-18) do tch mt phn t nc. Cc andehid thm cho ion phn t M+ v cc ion (M-H)+ , (M-CHO)+, 91, 77, 65, 51, 39,...

Hnh 3.4.1. Ph khi ca 3-phenyl propen-2-al3.4.2. Xeton3.4.2.1. Xeton mch thng

Ion phn t trung bnh n yu. Cc ion thng xut hin trn ph l m/e 43, 57, 58, 71, 72, 86,..S ion ha phn t thng xy ra theo c ch F5 cho cng mnh thng l ion c s (100%), s chuyn v nguyn t H theo c ch chuyn v H1 cho ion cng thp.

3-Phenyl-2-propenal (C9H

8O) MW = 132.16

Khi ph Trang 23

Hnh 3.4.2. Ph khi ca 4-heptanon

3.4.2.2. Xeton mch vngIon phn t ca xeton vng lun c cng mnh, s ph hy phn t thng

xy ra lin kt C-C gip nhm C=O3.4.2.3. Xeton thm

Ion phn t ca xeton thm Ar-CO-Ar v Ar-CO-R u c cng mnh, s ph v lin kt i vi nhm C=O l thun li i vi arylankyl hay diarylxeton cho ion Ar-CO+ cng nh Ar + hay R+, khi gc R t C3 tr ln th s ph v lin kt C-C v tr i vi nhm C=O l thun li.3.5. Ph khi ca este3.5.1. Este ca axit mch thng bo ha

Ion phn t ca este c cng yu hoc vng mt, cc s khi thng xut hin m/e 59, 60, 74, 88,... S ph v phn t thng theo c ch ct F1 hay chuyn v Mc.Lafferty H1.

O

O

R

R

OH

O

R1 OH

OH

OHR

O

m/e 74, 88, 102

m/e 61, 75, 89

m/e (27 + R)

m/e 61

O

OH

m/e 60

F5

F5+

+

+

+

+

+H1

H1

2H

2H

2HTch gamma

C ch quan trng l tch onium F5, chuyn v Mc.Lafferty H1 v chuyn v (2H). i vi cc este mch di c c ch tch gamma gi mt vai tr quan trng.

Ethyl acetate (C4H

8O

2) MW = 88.11

Khi ph Trang 24

Hnh 3.5.1. Ph khi ca etyl acetat

3.5.2. Este ca axit thmIon phn t ca axit thm c cng mnh, khi mch cacbon ca nhm ankyl

cng di cng ca ion phn t cng mnh, ion c s c hnh thnh do ct t OR hay ct COOH cho cc ion dng (M-OR)+ v ion dng (M-COOR)+. Mch cacbon ca gc ancol c th b ct theo 3 hng ca chuyn v H1 v ct F(3)3.5.3. Lacton

Ion phn t t vng 5 vi nhm th ankyl v tr C4 c cng yu, s ph v phn t theo hng ct t C-O m vng, sau ct lin kt C-C cho ion (M-R)+.3.6. Ph khi ca axit cacboxylic3.6.1. Axit cacboxylic mch thng bo ha

Ion phn t c cng yu hoc vng mt. Cc ion thng xut hin l m/e 45, 60, 73, 87,...

S ph v phn t ch yu xy ra theo c ch chuyn v McLafferty H1 cho ion c cng mnh. C ch F1 cng xy ra vi lin kt C-C v tr .

Hnh 3.6.1. Ph khi ca 2-butenoic axit

3.6.2. Axit cacboxylic thmAxit cacboxylic thm cho ion phn t c cng mnh, cng cho cc ion (M-

17)+ do ct OH, (M-45)+ do ct COOH, (M-18)+ do ct H2O.

2-Butenoic acid (C4H

6O

2) MW = 86.09

Khi ph Trang 25

V. BI TP NG DNGPhn tch ph khi lng l tm mi lin quan gia cc s khi xut hin trn ph

khi lng v cu to phn t da trn c ch ph v phn t. Cng thc ny khng phi lc no cng c th gii quyt thun li v trn vn c n ph thuc vo tng trng hp c th, nhn chung c th phn ra cc trng hp sau:

- Trng hp th nht: c cng thc d kin cn da vo ph khi lng xc nh cng thc c ng khng. Trng hp ny tuy n gin nht, trc tin cn tm trn ph c s khi tng ng vi phn t lng, tuy nhin c trng hp xut hin trn ph nhng c nhiu trng hp vng mt do phn t ln d b ph v phn t khng bn. Trng hp phn t c cha cc nguyn t Cl, Br, S c th da vo chiu cao pic ion phn t ng v xc nh. Sau t cng thc phn t, da vo c ch ph v tm kh nng cc ion mnh hnh thnh ri tnh s khi ca ion, sau i chiu vi cc gi tr m/e trn ph xem c trng khng. Nu s khi phn t tm c trn ph v c s trng lp ca mt s ion mnh th c th xc nhn cng thc cu to d kin ca cht l ng.

- Trng hp th hai: bit khi lng phn t v cng thc cu to phn t phi da vo s khi m/e trn ph v cu to ca cc mnh ion c s khi lp ghp li thnh phn t.

- Trng hp th ba: bit khi lng phn t phn gii cao ( v d M= 151,0634) c th da vo bng tra cu tm ra cng thc phn t, sau tin hnh nh trng hp trn.

- Trng hp th t: bit khi khi lng phn t v cc loi nguyn t c mt trong phn t, trc tin nn da vo cc ion ng v ca Cl, Br, S nu phn t c cha cc nguyn t ny v t l ng v 13C/ 12C xy dng cng thc phn t, sau cng da vo s khi m/e trn ph thit lp cng thc cu to nh trn.* Cc bc xc nh cng thc cu to ca mt hp cht:- Xc nh khi lng ion phn t M+- Xc nh khi lng cc mnh ion.- Xc nh hiu s khi lng ca ion phn t v cc ion mnh.- Tm cc pic (M+1)+ v (M+2)+, xc nh t l cng ca cc pic ny vi pic M+- Ghi th hiu cc ion mnh.MT S BI TP T LUNBI TP 1: Ph khi ca mt s cht cha bit (hnh 5.1) cho ion metastabilm* : 162.3; 73.6; 56.46Phn tch nguyn t 74.0%C, 5.6%H, 6%N, 14.0%O.Thit lp cng thc cu to ca hp cht.

Khi ph Trang 26

Hnh 5.1

Giim/e 239 197 162 141 120 105 92197 42162 77 35141 98 56 21120 119 77 42 21105 92 57 36 1592 105 70 49 28 13

64 43 28 1555 40 27

- Trng lng phn t l 239 cha s l nguyn t nit- T phn tch nguyn t = khi lng phn t C15H13O2- T m/e 51, 65, 77 vng thm (nhn phenyl)- m/e 105 77 (m* = 56,4 ) benzoyl C6H5-CO- m/e 43 axetyl CH3-CO- lin h vi oxi hay nit phn t. V hp cht ch cha hai oxi nn nhm CH 3-CO- phi gn vi nit. C6H5-CO- -HN-CO-CH3- C7H5O m/e 105 m/e 58 C2H4O ------------ C9H9O2 cn li C6H4-Vy C6H4- l mt nhn thm v c cng thc l:

C

O

NH C CH3O

Khi ph Trang 27

C

O

NH C CH3O

43105

162

BI TP 2: Xc nh cng thc cu to ca ancol c ph khi cho hnh 5.2

Hnh 5.2 Gii

- i vi ancol, ion phn t c cng yu M=86, l ancol khng no c th gi thit cng thc cng C5H10O = 86- m/e 71 = (M-15), m/e = (M-43), m/e 59 =(M-27)

CH3 C OHH2C CH

C th gi thit bn cng thc

Khi ph Trang 28

CH2CH C CH3

OH

CH CH

OH

CH3

CH CH3CH3

CHCH2 CH

OH

CH2

CH3

OH

CH2CH

CHCH2

CH3

(1)

(2)

(3)

(4)

- Cng thc (3) v (4) b loi tr v khng gii thch c s tn ti ca m/e 59 = (M- C2H3)

- Cng thc (1) phi tn ti m/e57 = (M- C2H5) nhng ph khng c- Vy cng thc tn ti thch hp l (2)

BI TP 3: Xc nh cng thc cu to ca mt cht cha C, H, S hoc Si, ph khi hnh 5.3

Hnh 5.3Gii

Lp bng tnh hiu s m/e:

m/e 120 105 92 87105 1592 28 1387 33 18 5

Khi ph Trang 29

73 47 32 19 1464 56 41 28 2361 59 44 31 26

Ion phn t M+ = 120, ion c khi lng nh l 46 v 61. T l cng (M +2)/M chng t cht cha 2S hay 2Si nhng khng th c mt Si bi v nu c Si th vch (M+1) phi ln hn vch (M+2) v 29Si chim 5.1% , 30Si chim 3.4% nhng trn ph vch (M+2) ln hn (M+1). Do cng thc tng ca n c th l C5S2 l khng c, trng lng phn t ca C5S2 l 124 ln hn d kin cho. Cn gi thit C3H20S2 hay C3H40S2 u khng th. T cng thc C4H8S2 c th gi thit cng thc cu to sau:

SSH

S

S SSSS S

SS

S

S

S

S

S

S

47 91

SH

59 61

(1) (2) (3)

(4) (5) (6)

(7) (8) (9)

T 9 cng thc cu to gi thit th vic khng nh mt cng thc no l chc chn th qu l kh khn. Tuy nhin da vao ph c th loi bo cng thc 7 v 8 (v ion 105 trn ph qu yu) v cng thc 5 (tch C2H4 l khng th)Bng mt s phng php ph khc na ngi ta khng nh cht nghin cu c cng thc cu to 9.BI TP 4: Ph khi ca mt cht cha bit c s khi phn t M= 152,0470 (hnh 5.4). Xc nh cu to ca cht.

Khi ph Trang 30

Hnh 5.4Gii

Tra cu trn bng thy ng vi cc s khi:m= 152,0460 (m= -0,0010) l C6H6N3O2m= 152,0473 (m= +0,0003) l C8H803Ta s chn cng thc phn t l C8H803 v c mnh hnTrn ph c m/e = 152(M+); 121; 120; 90;65 c th gii thch nh sau:m= 152-121=31, ct nhm -OCH3m= 120-92=28. ct nhm C=OChng t phn t c nhm

Ion m/e=92 c cu to:

Do kt hp cc nhm cho thy cng thc cu to ca hp cht nh sau: metylsalixilat

BI TP 5: Ph khi lng ca mt cht bit cho ion phn t M+= 100,0523 v cc s khi m/e= 85; 5(100); 43; 41; 29 (hnh

5.5). Xc nh cng thc phn t.

CO

OCH3

OH

O+

C6H4O+

CO

OCH3

Khi ph Trang 31

Hnh 5.5Gii

T bng cho thy ng vi m= 100,0523 v y m= 100,0524- 100,0523= 0,0001 nn cng thc phn t ca cht chnh l C5H8O2m= 100-85=15 ->CH3+m= 100-56=44 -> CH3-CH=O+m/e= 56 -> C4H8+Cu to phn t d kin l:

CH3 C

H

CH2CH3

C CH3

O+

-15

CH3 C

H

CH2CH3

C CH3

O

M+=100m/e 85

CH3 C CH2+

CH3

+ CH3 CH O + CH3 CH OCH3 CH CH2CH3

+

m/e 56 m/e 44

BI TP 6: Gii thch cu to ca cc hp cht c ph khi cho hnh 5.6.

Khi ph Trang 32

Hnh 5.6Gii

m/e 83/85/87 CHCl2m/e 131/135/137 3Cl + C2H2M* 166/168/170 (cha 4Cl)Cu to: CHCl2-CHCl2 (1,1,2,2- tetracloetan)

BI TP 7: Gii thch cu to ca hp cht c ph cho hnh 5.7

Khi ph Trang 33

Hinh 5.7Gii

m/e 185= (M-16), 171= (M-30), 155= (M-46) NO2M+ 201/203 (cha 1 Br)Cu to:

NO2Brp-nitrobrombenzen

BI TP 8: Gii thch cu to ca hp cht c cng thc phn t C8H16O v ph khi hnh 5.8.

Giim/e 57 C4H9+m/e 29 C2H5+m/e 99= (M-29) C4H9-+COCu to:

CH3CH2 C

O

CH2 CHCH3CH3

Etylisobutylxeton

Khi ph Trang 34

TI LIU THAM KHO

1- Cc phng php phn tch VT L V HA L (Tp 2) PHNG PHP PH KHI LNG _ GS TSKH Nguyn nh Triu _ NH XUT BN KHOA HC K THUT.2- KHI PH_L thuyt Bi tp Bi gii. Nguyn Kim Phi Phng _ NH XUT BN I HC QUC GIA TP H CH MINH.3- Phn tch ha l Cc phng php ph nghim nghin cu cu trc phn t. GS TSKH T Vn Mc _ NH XUT BN KHOA HC K THUT.4- Cc phng php vt l ng dng trong ha hc. Nguyn nh Triu _ NH XUT BN I HC QUC GIA H NI.5- http://www.chem.arizona.edu