287

THE MASS SPECTRA OF DIMETHOXYAMPHETAMINE HYDROCHLORIDES

The mass spectra of several derlvatlves of phenethylammc have been re- ported’ -’ Bellman” described the spectra of the hallucmogemc mcthoxylated derlvatlvcs 3.4.5-trlmethoxyphcnethylum~ne(mescal~ne)und 2.5-dlmcthoxy-4-mcthyl- amphetamine (DOM or STP) and accounted for their prlnapal fragmentation pathways The “P-fission” process (/j to the amino function and to the benzene ring) IS the common and maJor cleuvagc mode of amphetwmmes’ -’ In the present work. the effect of the arornatlc substitution pattern on the fragmcntatlon of dlmcthoxy- amphctamlncs was cxammed. and the mass spectra were studled for thclr sultabihty for ldentlficatlon and dlffcrentlatlon of these halluanogenlc’ compounds

The normall~ed mass spectra obtatned from the SIX pos\lblc dlmcthoxy- amphctamlnc hydrochlorldes (the\c salts are more cas~ly mamtalned m ;t pure state than arc the free bases) are presented m Figs. l--6 All have HI/C 44 as the base peak, a weak parent ion at m/c I95 equlvalcnt to that from the free amme. and only two or three other peaks greater than 5”,, Thus It 1s Important to know that the mass spectrometer does not show signals from residual substances The spectra, although weak and similar. seem to be characteristic. but observations made at such low relative abundances require careful assessment

The side-chain cleavage modes shown in the scheme were proposed by Beckett ~JI (11.’ but no metastable Ions supporting these contentlons were reported.

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Cleavage cd to give ,~-15 probably occurs weakly in all, but the corrcspondmg metastable ion at m/e 166.2 was not observed for any isomer Bellman3 considered that ~-15 m DOM probably arose by loss of the aromatic methyl rather than cleavage (I. Loss of a methyl radical from a methoxy group might be more favoured In the 2,3- 2,5- and 3,4-Isomers since these could form qulnold-stabilized lomc species”.

A rurl C/II/H 4 < ta. 60 ( 1972)

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Clcuv~~gc h 15 the domtnant lragmcntatton process and 1s rc\ponsiblc for the base peak at r~/e 44 The po\ltlvc charge 1~s with the ITT/C’ 151 dlmcthoxytropyllum fragment 111 the 2,4-isomer more than In the others

Cleavage c would glvc the dlmcthoxyphcnyl ion with m/c 137 In no case was the corrcspondlng mctastablc Ion (calculated t~/o 96 3) observed, but tht* meta\table ion at IV/C’ 123 5 seen in every spectrum Is approprlatc for the production of nz/o 137 from ttl/e 152 The wcukncs4 of UZ/V 137 and of the mctustablc ion at 123 5 m the 3.5-tsomcr perhap\ rcflccts the Inablllty of the oxygen atoms 111 thcsc posItion\ to stublli/c the posltlvc charge dcvclopcd on CI

The rcmalnlng Important fragmentation proccs\es involve the aromatIc ring sub\tItt,cnts and rcarrungcmcnt procc\scs

W/V 164 Thl4 15 comparatlvcly abundant HI the 2,3-Isomer and here only was ;I (weak) mcta\tablc Ion at 138.0 (as calculated for 111-31) seen It 14 tentatlvcly \ug- gcstcd that bond-strarns assoclatcd with 1,2,3-trlrubstltutlon of the bcnzenc ring ale rc\ponslblc for this dlffct cncc, although m/c 164 IS very wcnk In the 2.6-1~0111~1 The

3-mcthoxy rudtcal may bc the one mostly cxpcllcd SIIICC this would give an orrllo substltutcd -ion. Only the 2,3-lsomcr cxhlblted ;I mctastuble ion at rtz/cj 136 4, the poc;ltion calculated for I95 fragtncntlng to in/c) 163 (loss of CHJOI-I) IS 136 3

rn/cj 152 This IS the second most Important signal 111 the spectra It corresponds with protonatcd dnnethoxytropyl~um or dlmcthoxybenzyl ion, and the mctastablc 1011 at m/e 118.4 for 111-43 (loss of Cl-I ,CH=NH) was obscrvcd 111 every \pccttum. Hellman proposed’ that such ions ;LIOSC by amino proton transfer to the bcn/yllc position, glvlng a structure such as

Thcrc IS no cvldcncc for the altctnutlvc McLalfcrty arrangement to a species such its

since the 2,6-isomer appears to be uncxccptlonal. and a subscqucnt breakdown path IS the loss of 15 mass units (CH,) to give UI/P 137 as dcscrtbed earllcr In the 2,4- and 2,5-lsomcrs the W/C 152 ion 1s partlculally abundant

m/e 121 This corresponds with loss of 31 (CH,O) from m/e 152 or of 43 (CHJCH=NH) from m/e 164, but metastable ions at the calculated posttlons (96.3 and 89.3 respectively) were not observed. A metastable ion at 97.0 was seen in the

MASS SPEC’THA S 291

2,4- and 2.5-isomers and wenkly In the 2,6- ,md 3.5-Isomers and not m the 2.3- or 3,4-isomers IX, In a strength roughly proportional to the lntenslty of the tlt/c~ 121 pc;th The calculated posltlon for 11 metastable Ion associated wtth the production of m/c I21 from 151 IS 97.0. A metastable Ion was noted at m/e 75.3 m the 2.5- and at 75.6 In the 2,3-, 2.4-. and 2.6-Isomers Breakdown of the molecular ton to jn/e 121 would have the metastablc Ion at (calculated) 75 1 : loss of a nitrogen-contammg fragment ol 74 maFs units (CJH,NO”) lndlcates a process lnvolvlng the side chain and methoxyl molctles However, the fragmentations t?l/e 109 to fin/~’ 91 dnd In/c> 108 to m/c 90 have metastable po\:trons calculated at 76 0 and 75 0 rcspecrlvcly

IP~/P 91 The production of the tropyllum ion )PI/~J 91 by loss of 30 mass umts (CH,O) from I~/CJ 121 1s normal, and the correspondmg metu\table ion WILS observed at 68.5 for all but the 2,3-Isomer which has ~1 very weak m/e 121 The breakdown of tropyllum 14 well established’

The broad. weak. ovcrlapplng mctastable Ions seen In every cast at ,n/c 86 5- 87 5 are probably associated with fission of the fragments around 111/e 137 to those around I09

In conclusion. the mass spectra of the d~methoxyamphctamlne hydrochlorldes offer a ready method for detcrmlnlng the character of a substance to be that of a dlmcthoxyamphctamlne. ;lnd spectral dlffercnces Incllcate that substlluent rundom- tzatlon IS not too slgmficant However. their general wcakncss does not support confidence m mass spectrometry alone for unequlvocol Idcntlficatlon of the mdlvldual Isomers, espcc~ally if small cluantttles of extraneous substances with possibly strong spectra are present In the sumplc or resrdual m the spectrometer It seems very desirable that the Investigator have authcntlc material for simultaneous comparison on the same spectrometer

Mas\ spectra were recorded on an A E 1 MS 12 with an ronlzatlon voltage of 70 eV and ;I probe temperature between 120 and 1 JO” The salts described here were syntheszcd by st‘lndard procedures ;tnd rccrystalhzcd from lsopropanol- hexanc to constant m p

The skllful tcchnlcal :lsslst:mcc of Mllc D Verner of these laboratortcs 1s gratefully .uzknowlcdged Muss spectra were measured by Mr .I Cashmorc of the Chemistry Department, Trent Unlverslty, Pctcrborough, Ontario, whom I thank

SUMMARY

The SIX dlmethoxyamphetamme hydrochlorldcs give weak but dlstmguishablc mass spectra useful for analytical purposes The prmclpal fragmentatron pathways are discussed in terms of the changing aromatic substitution pattern

Les hydrochlorures des SIX dlm~thoxyarnph~tammes donnent des spectres dc masse pauvres, mals dlstmcts, utlles pour fins analytlques. Les fragmentations prmclpales sont exammkes en fonctlon du type de substitution aromatlque

K HAILEY

DIG sechs D~methoxyamphctam~nhydrochlor~dc ergcben schwachc. aber unterschctdbarc Masscnspcktren, die fur analytlsche Zwccke verwcndet werden konnen DIG wcsentllchcn Fragmcntlerungswege werden Irn Zusammenhang mlt der ilnderung des aromatlschcn Substltutlonsschemas dlskutiert.