Syntheses of 12-aminododecanoic and 11-aminoundecanoic acids from vernolic acid

Article abstract of DOI:10.1007/s11746-997-0176-z

12-Aminododecanoic acid and 11-aminoundecanoic acid, monomer precursors for nylon-12 and nylon-11, respectively, have been synthesized from vernolic (cis-12,13-epoxy-cis-9-octadecenoic) acid via a reaction sequence that includes the formation of 12-oxododecanoic acid oxime. Saponification of vernonia oil, followed by a low-temperature recrystallization at -20°C, gave 51% vernolic acid (97% purity, m.p. 23-25°C). Hydrogenation afforded cis-12,13-epoxystearic acid (m.p. 52-54°C, lit. m.p. 52-54°C), which upon oxidation with periodic acid in tertiary butyl alcohol gave 12-oxododecanoic acid with an isolated yield of 71.0%. Reaction of the oxoacid with hydroxylamine hydrochloride gave 12-oxododecanoic acid oxime, which was catalytically reduced to give 12-aminododecanoic acid with a yield greater than 85% and a melting point of 184-186°C (lit. m.p. 185-187C). 11-Aminoundecanoic acid was prepared from the 12-oxododecanoic acid oxime via a three-step reaction sequence that involved a Beckmann rearrangement, Hofmann degradation, and hydrolysis. Thus, the aldoxime acid was hydrolyzed in the presence of nickel acetate tetrahydrate to give 11-carbamoylundecanoic acid (48% yield, m.p. 129-131°C, lit. m.p. 129-130°C). The amide was then treated with a solution of sodium methoxide and bromine at 70-80°C to give 11-(methoxycarbonylamino)undecanoic acid at 75% yield (m.p. 84-86°C; elemental analysis, calculated for C₁₃H₂₅NO₄: C, 60.19; H, 9.73; N, 5.40; O, 24.68%; found C, 60.02; H, 9.81; N, 5.26; O, 24.91%), which upon alkaline hydrolysis and subsequent neutralization gave 11-aminoundecanoic acid at 34% yield (m.p. 189-192°C, lit. m.p. 190°C). Mass spectrometric and ¹³C nuclear magnetic resonance data of the previously unreported 11-(methoxycarbonylamino)undecanoic acid is provided.

Full text of DOI:10.1007/s11746-997-0176-z

Syntheses of 12-Aminododecanoic
and 11-Aminoundecanoic Acids from Vernolic Acid
Folahan O. Ayorinde*, Erick Y. Nana, Pete D. Nicely, Anthony S. Woods,
Elvis O. Price, and Chukwuma P. Nwaonicha
Department of Chemistry, Howard University, Washington, DC 20059
ABSTRACT: 12-Aminododecanoic acid and 11-aminounde- ings, plasticizers, stabilizers, and syntheses of industrial
canoic acid, monomer precursors for nylon-12 and nylon-11, re-
spectively, have been synthesized from vernolic (cis-12,13-
epoxy-cis-9-octadecenoic) acid via a reaction sequence that in-
cludes the formation of 12-oxododecanoic acid oxime.
Saponification of vernonia oil, followed by a low-temperature re-
crystallization at −20°C, gave 51% vernolic acid (97% purity,
m.p. 23–25°C). Hydrogenation afforded cis-12,13-epoxystearic
acid (m.p. 52–54°C, lit. m.p. 52–54°C), which upon oxidation
with periodic acid in tertiary butyl alcohol gave 12-oxodode-
canoic acid with an isolated yield of 71.0%. Reaction of the oxo-
acid with hydroxylamine hydrochloride gave 12-oxododecanoic
acid oxime, which was catalytically reduced to give 12-aminodo-
decanoic acid with a yield greater than 85% and a melting point
of 184–186°C (lit. m.p. 185–187°C). 11-Aminoundecanoic acid
was prepared from the 12-oxododecanoic acid oxime via a three-
step reaction sequence that involved a Beckmann rearrangement,
Hofmann degradation, and hydrolysis. Thus, the aldoxime acid
was hydrolyzed in the presence of nickel acetate tetrahydrate to
give 11-carbamoylundecanoic acid (48% yield, m.p. 129–131°C,
lit. m.p. 129–130°C). The amide was then treated with a solution
of sodium methoxide and bromine at 70–80°C to give 11-
(methoxycarbonylamino)undecanoic acid at 75% yield (m.p.
84–86°C; elemental analysis, calculated for C13H25NO4: C,
chemical intermediates (1–3). Vernolic acid, the major acid
component of vernonia oil (VO), was first characterized from
V. anthelmintica oil by Gunstone (4) as cis-12,13-epoxy-cis-
9-octadecenoic acid. Bharucha and Gunstone (5) also demon-
strated the presence of the acid in Cephalocroton cordofanus
oil, and Chisholm and Hopkins (6) indicated occurrence of
the acid in the oil of Hibiscus esculentus. Isolation and iden-
tification of vernolic acid from V. anthelmintica seed oil was
earlier reported by Smith, et al. (7), Krewson (1), and by
Chisholm and Hopkins (8).
In the present work, we report the syntheses of 12-aminodo-
decanoic acid and 11-aminoundecanoic acid, monomer precur-
sors for nylon-12 and nylon-11, respectively. Nylon-12 is an
engineering polyamide used as a curing agent for epoxy resins
or as modifiers for polyester (9). This polymeric material also
has applications in the automobile industry for the preparation
of oil- and gasoline-resistant hoses. Other applications of
nylon-12 include its use in hydraulic systems, electrical cable,
metal coatings, ship propellers, screws, injection syringes, ster-
ilized films and bags for medical purposes, and for sausage skin
(10). Furthermore, modification of these nylon-12 products can
60.19; H, 9.73; N, 5.40; O, 24.68%; found C, 60.02; H, 9.81; N, be effected by the addition of some polyamide additives such
5.26; O, 24.91%), which upon alkaline hydrolysis and subse-
quent neutralization gave 11-aminoundecanoic acid at 34% yield
as plasticizers, pigments, heat, and light stabilizers.
The preparation of nylon-12 was first mentioned by
Carothers (11). By trimerizing butadiene, Ziegler and Wilke
(12) prepared cyclododecatriene, which was subsequently
converted to nylon-12 through a series of reactions. The buta-
diene is produced mostly from petroleum gases by catalytic
dehydrogenation of butene or butene–butane mixture, or al-
ternatively by cracking naphtha (C6H14–C7H18) or light oil.
Several other methods for synthesizing 12-aminodode-
canoic acid have been reported in the literature. For example,
11-formyl-4,8-undecadienoic acid was reacted with aqueous
ammonia and 30% sodium hydroxide, with subsequent reduc-
tion of the imine (13). Hawkins and coworkers (14) reduced
(m.p. 189–192°C, lit. m.p. 190°C). Mass spectrometric and 13
C
nuclear magnetic resonance data of the previously unreported
11-(methoxycarbonylamino)undecanoic acid is provided.
JAOCS 72, 531–538 (1997).
KEY WORDS: Aldoxime, 12-aminododecanoic acid, 11-
aminoundecanoic acid, Beckmann rearrangement, cis-12,13-
epoxy-cis-9-octadecenoic acid, 12,13-epoxystearic acid, 12-
oxododecanoic acid, 12-oxododecanoic acid oxime, vernolic
acid, vernonia oil.
Current interest in Vernonia galamensis seed oil (vernonia 11-cyanoundecanoic acid, obtained by vapor-phase pyrolysis
oil) derives from its naturally epoxidized triglyceride fatty of 11-peroxydicyclohexylamine at 300–1000°C, to yield 12-
acids, giving it potential as a unique oil for industrial raw ma- aminododecanoic acid. Also, Tsyskovskii and Razumovskii
terials used in plastic formulations, adhesives, chemical coat- (15) treated the monoozonide of a cycloolefin or cyclopoly-
olefin with hydroxylamine and reduced the resulting oxime.
Bacterial conversion of dodecamethylenediamine to 12-amino-
*To whom correspondence should be addressed at Department of Chemistry,
Howard University, 525 College St., NW, Washington, DC 20059.
dodecanoic acid was cited by Matsumoto (16).
Copyright © 1997 by AOCS Press
531
JAOCS, Vol. 74, no. 5 (1997)

532
F.O. AYORINDE ET AL.
Nylon-11 (tradename Rilsan) is an engineering resin that roform-d (CDCl3) and methanol-d4 (CD3OD) as solvents and
is used in various engineering plastics because of its excel- sources of internal standards. Melting points (m.p.) were de-
lent dimensional stability, abrasion, and vibration resistance. termined on a mel-temp II capillary m.p. apparatus.
Other uses include electrical (cable extrusion), mechanical
Saponification of VO. To a 250-mL distilling flask,
(molding intricate components), and sports equipment and in- equipped with a magnetic stir bar, was transferred 50 mL
dustrial fabrics, powder coatings and synthetic fibers. Cur- methanol and 4.97 g (0.124 mol) sodium hydroxide. The flask
rently, castor oil is the only source of this versatile polymeric was then fitted with a condenser, and the mixture was heated
resin. The synthesis of nylon-11 from castor oil involves at to reflux until complete dissolution of the sodium hydroxide.
least six reaction steps, one of which is the energy-intensive To the hot alkaline solution was added, in one portion, 5.12 g
pyrolysis (450–500°C) reaction.
(5.5 × 10−3 mol) VO. The resulting brownish solution was re-
In this communication, we present experimental results fluxed with continuous stirring for 10 min, after which it was
that demonstrate the potential use of vernonia oil in the pro- immediately transferred into a beaker and allowed to form a
duction of both nylon-12 and nylon-11 monomers. For both semisolid on cooling. About 100 g ice was added, mixed thor-
monomers, the key intermediate was 12-oxododecanoic acid oughly, followed by addition of 100 mL water with mixing.
oxime. For the nylon-11 monomer, the acid oxime was con- The cold mixture was vacuum-filtered to afford an off-white
verted to the amide (11-carbamoylundecanoic acid), which solid soap in the filter bed.
subsequently underwent Hofmann degradation to give the 11-
The soap was transferred into a beaker and mixed with ca.
aminododecanoic acid. Earlier synthesis of 11-carbamoylun- 100 g ice and 100 mL water, then acidified with ca. 4 mL
decanoic acid had been reported in a British patent by acetic acid. The acidified mixture was immediately vacuum-
Durston (17). In his work, 1,1-peroxydicyclohexylamine was filtered to afford a white solid (containing a mixture of acids).
thermally decomposed below 450°C to give decane-1,10-di- The cold white solid was transferred into a beaker, containing
carbonimide, which was subsequently hydrolyzed to obtain 100 mL hexane, with mixing to dissolve the acid, and the re-
the amide. Also, Kataoka and Ohno (18) synthesized 11-car- sulting mixture was transferred into a separatory funnel to
bamoylundecanoic acid from a cyclic hydroxyimino ketone allow separation of the organic and aqueous phases. The
by treatment with concentrated sulfuric acid. Thus, our inves- hexane layer was stripped to afford crude vernolic acid (4.5
tigation represents the first reported syntheses of both 12- g).
aminododecanoic acid and 11-aminoundecanoic acid from a
Gas-chromatographic analysis of the methylated crude
single source, vernolic acid, via the intermediacy of 12-ox- product indicated palmitic, oleic, linoleic, stearic, and verno-
ododecanoic acid oxime.
lic acids. Mass spectral data of the methyl vernolate were con-
sistent with previously reported data (19).
Purification of vernolic acid. The vernolic acid isolated
above was 76% pure, based on the oxirane value of 4.1%. Pu-
EXPERIMENTAL PROCEDURES
The crude VO that was used in this project was obtained from rification of the acid was accomplished by low-temperature
IXTT Corporation (Culver, IN). Reactions and products were recrystallizations. Hexane (50 mL) was added to a 150-mL
monitored with a Finnigan gas chromatograph (model 9611), beaker containing 4.5 g of the crude vernolic acid, and the
equipped with a splitless injector and interfaced with a Finni- beaker was then placed in a −20°C freezer for 24 h. The re-
gan MAT 4500 automated mass spectrometer with a SUPER- sulting solid was vacuum-filtered and rinsed with an addi-
INCOS data system (San Jose, CA). The interface oven and tional 50 mL ice-cold hexane to give 2.77 g (56.72% yield)
transfer line were maintained at 300°C, the ionizer tempera- vernolic acid (m.p. 23–25°C, lit. m.p. 25–28°C, oxirane %
ture setting was at 150°C, with electron impact (EI) mode, 5.22, 96.0% purity).
with emission current 0.39 mA, electron multiplier 1500 V
Preparation of cis-12,13-epoxystearic acid. A 2.6-g (8.8 ×
and electron energy at 70 eV. High-resolution capillary gas 10−3 mol) sample of vernolic acid was placed in a Parr hydro-
chromatography was conducted with a Supelco fused-silica genation bottle, followed by 0.03 g (1.3 × 10−4 mol) platinum
SPB-1 (30 m, 0.32 mm i.d., 0.25 µm film) column (Belle- oxide (Adam’s catalyst) and 15 mL methanol. The bottle and
fonte, PA), oven temperature was programmed from 50 to its contents were fitted to a Parr high-pressure system (Mo-
300°C, and helium was used as the carrier gas with a head line, IL). The air in the bottle was evacuated with a water as-
pressure of 10 psi. Characterization of the acids by gas chro- pirator, after which the bottle was filled with hydrogen gas to
matography/mass spectrometry (GC/MS) was performed maintain a pressure of 3 atm for 45 min with continuous shak-
with methylated samples, prepared by adding 1 mL ethereal ing. After hydrogenation, methanol (15 mL) was added to the
solution of diazomethane to ca. 10-mg sample of acids. The reaction mixture, then heated to gentle boiling to dissolve the
infrared (IR) spectra were obtained on a Perkin-Elmer model product. The hot mixture was quickly filtered to remove the
983G spectrophotometer (Palo Alto, CA). Solid samples were suspension of black platinum, and the filtrate was evaporated
run with KBr, while liquid samples were run neat. The 13C to give 2.42 g (93% yield) of white solid, consisting of 99%
nuclear magnetic resonance (CNMR) and proton nuclear (GC purity) cis-12,13-epoxystearic acid after recrystalliza-
magnetic resonance (PNMR) spectra were recorded on a GE- tion from hexane (m.p. 52–54°C, lit. m.p. 52–53.5°C).
NMR QE-300 model spectrometer (Fremont, CA), with chlo-
Oxidation of cis-12,13-epoxystearic acid. A 2.40-g (0.008
JAOCS, Vol. 74, no. 5 (1997)

NYLON-12 AND NYLON-11 MONOMERS FROM VERNOLIC ACID
533
mol) sample of cis-12,13-epoxystearic acid was placed in a methanol in a 100-mL flask, equipped with magnetic stirrer,
250-mL Erlenmeyer flask and dissolved with 18 mL water condenser, and addition funnel. Alternatively, 11 mL 25 wt%
and 9 mL tertiary butyl alcohol. The mixture was stirred con- sodium methoxide/methanol (Aldrich Chemical Company,
tinuously for homogeneity, followed by addition of 1.95 g Inc., Milwaukee, WI) was transferred into the 100-mL flask.
(0.0086 mol) periodic acid in one portion. The reaction mix- The solution was cooled with ice to ca. 5°C. Then, a solution
ture was then stirred for 5 h, after which 150 mL ice-cold of 2.0 g (8.7 × 10−3 mol) amide in 10 mL methanol was added
water was added. The mixture was stirred for another 30 min, to the cooled sodium methoxide solution. To this mixture was
and the resulting solid was vacuum-filtered to give crude 12- added, with thorough mixing, 0.6 g (8.7 × 10−3 mol) bromine.
oxododecanoic acid. The acid was washed, then recrystallized The resulting solution was heated to 70–80°C in a water bath
with light petroleum (b.p. 35–60°C) to give 1.22 g 12-oxodo- for 15 min. The flask was cooled to 25°C, and the solution
decanoic acid (73% yield, m.p. 53–54°C).
was made acidic (litmus paper) with acetic acid. The solvent
Preparation of 12-oxododecanoic acid oxime. A 2.75-g was evaporated, and the resulting solid was rinsed with 50
(0.04 mol) sample of hydroxylamine hydrochloride was placed mL water to remove sodium bromide. The crude product
in a 250-mL Erlenmeyer flask, followed by 16.5 mL water and weighed 2.03 g (89.8% yield) and was recrystallized from 30
gentle warming of the contents of the flask. To the flask was mL ethanol/water mixture (1:1) to give 1.7 g methyl carba-
added 11 mL 10% sodium hydroxide and 1.1 g (0.005 mol) 12- mate (75% yield, m.p. 84–86°C). Elemental analysis: calcu-
oxododecanoic acid. Ethanol (15 mL) was added to give a clear lated for C13H25NO4: C, 60.19: H, 9.73; N, 5.40; O, 24.68%.
solution. The mixture was warmed in a water bath for 10 min Found C, 60.02; H, 9.81; N, 5.26; O, 24.91%.
after which it was cooled in an ice-bath. The resulting solid was
Hydrolysis of 11-(methoxycarbonylamino)undecanoic acid
filtered and dried to give 1.05 g of aldoxime acid. Recrystal- to 11-aminoundecanoic acid. A 1.0-g (3.9 × 10−3 mol) sam-
lization was carried out in water/ethanol mixture (4:1) to give ple of 11-(methoxycarbonylamino)undecanoic acid was dis-
0.92 g aldoxime acid (m.p. 104–106°C). Elemental analysis solved in 20 mL ethanol, which was then added to a solution
found: C, 62.65; H, 9.92; N, 5.72%. Calculated for of 2.0 g (5.0 × 10−2 mol) sodium hydroxide in 2 mL water.
C12H23NO3: C, 62.85; H, 10.11; N, 6.11%.
The mixture was refluxed for 17 h. The resulting gold-colored
Preparation of 12-aminododecanoic acid. In a Parr hydro- solution was cooled and neutralized with acetic acid to pH 7,
genation bottle was placed 0.92 g of 12-oxododecanoic acid then filtered to remove any salt. The filtrate was stripped to
oxime (4 × 10−3 mol), 10 mL methanol, and then 0.005 g (2.2 give crude amino acid, which was dissolved in 50 mL water,
× 10−5 mol) platinum oxide (Adam’s catalyst). The bottle was then cooled in ice before filtering to give 0.41 g (53%) of the
fitted to a Paar high-pressure system, deaerated, then filled amino acid. Recrystallization from 16 mL ethanol/water (3:1)
with hydrogen gas to maintain a pressure of about 3 atm for gave 0.26 g (34% yield) 11-aminoundecanoic acid (m.p.
1.5 h with continuous shaking. After hydrogenation, 10 mL 189–192°C, lit. m.p. 190–192°C).
methanol was added to the reaction mixture, then heated to
gentle boiling to dissolve the product. The hot mixture was
quickly filtered to remove the suspended black platinum, after
RESULTS AND DISCUSSION
which the filtrate on evaporation gave 0.85 g (92% yield) 12- Upon saponification and acidification, crude V. galamensis oil
aminododecanoic acid. Recrystallization was effected in usually contains about 75–80% vernolic acid. Thus, the first
ethanol/water mixture (1:1) to give 0.80 g (87% yield) 12- step in the present investigation was the isolation and purifi-
aminododecanoic acid (m.p. 184–186°C, lit. 185–187°C).
cation of the epoxy acid. We investigated several isolation
Isomerization of 12-oxododecanoic acid oxime to 11-car- techniques (i.e., extraction, chromatography, low-temperature
bamoylundecanoic acid. A 100-mL round-bottomed flask, crystallization) and found that low-temperature crystalliza-
equipped with a magnetic stirring bar, was charged with 5.00 tion was most efficient and cost-effective because it utilizes
g (2.18 × 10−2 mol) 12-oxododecanoic acid oxime, followed the least amount of solvent.
by the addition of 0.11 g (4.41 × 10−5 mol) finely ground
Scheme 1 depicts the synthetic transformation of vernolic
nickel acetate tetrahydrate, 0.5 mL piperidine, and 25 mL p- acid to 12-aminododecanoic acid. The hydrogenation step was
xylene. The resulting mixture was stirred continuously and generally quantitative; however, reaction time should not ex-
heated (110–115°C) for 24 h. The flask and its contents were ceed 1 h to avoid formation of hydroxy acids, presumably due
allowed to cool to room temperature with occasional stirring to catalytic opening of the epoxy functionality. The resulting
to facilitate crystallization of the solid product, which was fil- 12,13-epoxystearic acid was easily oxidized with periodic acid
tered and rinsed with 15 mL of ice-cold hexane. The crude to give 12-oxododecanoic acid and hexanal. In many instances,
amide weighed 3.0 g (60% yield, m.p. 124–126°C). Recrys- when the reaction was allowed to proceed for more than 5 h,
tallization from 20 mL ethanol/water mixture (4:1) gave 2.25 some dodecanoic acid and hexanoic acid were produced as a
g of 11-carbamoylundecanoic acid (45% yield, m.p. result of overoxidation of the aldehyde functionalities. On the
129–131°C, lit. m.p. 129–130°C).
other hand, efforts to keep the reaction time below 5 h resulted
Preparation of 11-(methoxycarbonylamino)undecanoic in incomplete reaction, in which case there was unreacted ver-
acid (methyl carbamate). Sodium methoxide in methanol was nolic acid. Thus, it is important to maintain a 5-h reaction time.
prepared by adding 0.6 g (2.6 × 10−2 mol) of sodium to 25 mL There was no attempt to isolate the hexanal.
JAOCS, Vol. 74, no. 5 (1997)

534
F.O. AYORINDE ET AL.
824 cm−1, and 846 cm−1 (epoxy group). The absorption at
1600 cm−1 in the spectrum of vernolic acid corresponds to the
olefinic carbons. The PNMR of vernolic acid and 12,13-
epoxystearic acid were closely related, except that the absorp-
tion due to the olefinic protons at 5.5 ppm was absent in the
spectrum of 12,13-epoxystearic acid. The epoxy protons at
2.9 ppm were present in both spectra. 13C NMR (proton-de-
coupled) of vernolic acid (Fig. 1) indicated the presence of
carbonyl carbon at 180 ppm and olefinic carbons at 124 ppm
and 133 ppm, and the carbons attached to the epoxy function-
ality appeared at 56 and 57 ppm. On the other hand, a com-
parison of the 13C spectrum of 12,13-epoxystearic acid (Fig.
2) revealed the absence of olefinic carbon. Another signifi-
cant difference in the spectrum is the single peak at 57 ppm
(epoxy carbons), suggesting that the two carbons on the
epoxy functionality of the 12,13-epoxystearic acid have an
identical electronic environment. Figure 3 shows the 13C
NMR of the 12-oxododecanoic acid. Two distinct peaks were
observed at 180 ppm (carbonyl carbon of the carboxylic acid)
and 203 ppm (carbonyl carbon of the aldehyde). The mass
spectral data of the 12-oxododecanoic acid indicated exten-
sive fragmentations with a base peak at m/z 74, due to McLaf-
ferty rearrangement. The peak at m/z 229 represents (M + 1)
ion. Other diagnostic ions are m/z 210 (M − H2O), m/z 200
(M − CO), m/z 179 (M − OCH3) and m/z 185 (M − CH2OH).
The 12-oxododecanoic acid shows an IR absorption at 3500
cm−1 that is characteristic of the O-H of carboxylic acids. The
PNMR data indicated the presence of a proton attached to the
aldehyde functional group at 9.3 ppm. The multiplets at
0.8–1.8 and 2.2–2.5 ppm were due to the methylene protons.
The IR spectrum of the aldoxime acid showed a carbon–ni-
trogen double bond (C=N) stretch at 1690 cm−1 and carbonyl
(C=O) absorption at 1700 cm−1. The O-H stretching vibrations
of both functional groups were observed at the 2950–3300 cm−1
region. Delineation of the syn/anti isomeric composition of the
aldoxime group was accomplished with 13C NMR studies. The
quantitative 13C NMR spectrum (Fig. 4) showed three absorp-
SCHEME 1
Conversion of the 12-oxododecanoic acid to its oxime was
undertaken in an acidic medium (pH 4–5) with hydroxyl-
amine hydrochloride as the nucleophilic agent. Lower pH
value reduces the nucleophilicity of the hydroxylamine,
thereby preventing the formation of the oxime. The reaction
usually resulted in more than 85% isolated yield of the prod-
uct. Subsequent hydrogenation of the aldoxime afforded, in
all cases, more than 90% yield of the 12-aminododecanoic
acid. The GC characterization of the 12-aminododecanoic
acid was performed after methylation with ethereal solution
of diazomethane, and we noted that the amino group was
methylated to form methyl N,N-dimethylaminododecanoate,
thus confirming the presence of the amino functionality.
The IR spectrum of both 12,13-epoxystearic acid and ver-
FIG. 1. Proton-decoupled 13C nuclear magnetic resonance spectrum of
vernolic acid. Peaks are referenced to CHCl3 at 77 ppm. Samples were
made to 10 wt% in CDCl3. Operating frequency was at 75.6 MHz.
Chemical shifts (δ = ppm): carbonyl carbon, 180; olefinic carbons, 124
nolic acid shows strong absorptions at 1700 cm−1 (carbonyl), and 133; epoxy carbons, 56 and 57.
JAOCS, Vol. 74, no. 5 (1997)

NYLON-12 AND NYLON-11 MONOMERS FROM VERNOLIC ACID
535
FIG. 4. Proton-decoupled 13C nuclear magnetic resonance spectrum of
12-oxododecanoic acid oxime. Peaks are referenced to CH3OD at 49.0
ppm. Samples were made to 10 wt% in CD3OD. Operating frequency
at 75.6 MHz. Chemical shifts (δ = ppm): carbonyl carbon, 178.018;
anti-oxime carbon, 153.011; and syn-oxime carbon, 152.462.
FIG. 2. Proton-decoupled 13C nuclear magnetic resonance spectrum of
12,13-epoxystearic acid. Peaks are referenced to CHCl3 at 77 ppm.
Samples were made to 10 wt% in CDCl3. Operating frequency at 75.6
MHz. Chemical shifts (δ = ppm): carbonyl carbon, 182; epoxy carbons,
58.
tion peaks due to sp2-hybridized carbons. The signal at 178.018 ester are (M + 1) ion at m/z 230, a base peak at m/z 30
ppm was attributed to the carbon of the carbonyl group, while (H2NCH2), and m/z 156 (M − [(CH2)6CO2CH3]). The tertiary
the signals at 153.011 and 152.462 ppm were assigned to the car- amino ester gave a molecular ion peak at m/z 257 and a base
bons of the anti- and syn-aldoxime groups, respectively, based peak at m/z 44 [(CH3)2N]. Other fragmentation ions were m/z
on a previous report (20) on the 13C NMR spectra of aldoximes, 58 [(CH3)2 - N-CH2]+, m/z 170 (M − 87) and m/z 212 (M −
which demonstrated that the resonances due to the anti isomers 45).
are slightly higher than the corresponding resonances from the
The IR of the 12-aminododecanoic acid exhibited an ab-
syn isomer. Thus, the 13C NMR spectrum (Fig. 4) indicated the sorption at 1646 cm−1 attributable to the C=O and at
ratio of syn/anti isomers was about 7:3, a ratio that was further 2900–3200 cm−1 owing to the O-H group. The usual -NH2
supported by gas chromatographic data.
group absorption was weak at 3300 cm−1 owing to the strong
The MS of both syn and anti isomers gave similar fragmenta- O-H absorption of the carboxylic acid group at this region.
tion patterns except that the syn isomer showed a base peak at m/z However, the -NH2 bending frequency was observed at 1508
74, and no molecular ion peak was observed owing to loss of OH cm−1, and the C-N stretching frequency produced a strong
to give the ion at m/z 226. On the other hand, the anti isomer peak at 1400 cm−1.
showed a base peak at m/z 59, which may be attributed to a
The synthetic sequence for the transformation of 12-ox-
McLafferty-type rearrangement that involves the oxime part of ododecanoic acid oxime to 11-aminoundecanoic acid is out-
the molecule. An (M + 1) peak was apparent at m/z 244 for the lined in Scheme 2. Isomerization (or hydrolysis) of the oxime
anti isomer.
to the amide was performed under neutral conditions because
The GC of the 12-aminododecanoic acid showed two it has been demonstrated that mineral acid catalysis of al-
peaks when methylated with diazomethane. These peaks cor- doximes results in the regeneration of the starting aldehyde
respond to primary amino ester H2N(CH2)11CO2CH3 and ter- (21). We first investigated the rearrangement of the aldoxime
tiary amino ester (CH3)2N(CH2)11CO2CH3. The diagnostic to amide under conditions similar to those of Leusink and co-
ions observed in the mass spectral data of the primary amino workers (22), in which the aldoxime was treated with a cat-
alytic amount of nickel acetate and refluxed in p-xylene for 5
h. We found that the reaction did not go to completion under
these conditions, and that only traces of the product were iso-
lated. Moreover, a tar-like reaction mixture was obtained,
suggesting the possibility of some polymerization. Hence, the
temperature for subsequent reactions was maintained at
110–115°C, and the reaction time was increased to 24 h to
give 48% yield of 11-carbamoylundecanoic acid (m.p.
129–131°C, lit. m.p. 129–130°C). This relatively low yield
was attributed to the fact that the aldoxime was a mixture of
syn- and anti-isomers (ratio 7:3). GC/MS analysis of the re-
action mixture indicated that the anti-isomer was mostly un-
reacted, a finding that is consistent with reported studies indi-
cating that Beckmann rearrangement reactions generally
FIG. 3. Proton-decoupled 13C nuclear magnetic resonance spectrum of
12-oxododecanoic acid. Peaks are referenced to CHCl3 at 77 ppm.
Samples were made to 10 wt% in CDCl3. Operating frequency at 75.6
MHz. Chemical shifts (δ = ppm): carbonyl carbon of the aldehyde
group, 203; carbonyl carbon of the acid group, 180.
favor the isomerization of the syn-isomer. However, there are
JAOCS, Vol. 74, no. 5 (1997)

536
F.O. AYORINDE ET AL.
FIG. 5. Mass spectrum of methyl 11-carbamoylundecanoate: m/z 244
(M + 1), m/z 59 ([H2NC − CH2]H+), m/z 212 (M − OCH3), m/z 184 (M
− CO2CH3) and m/z 170 (M − CH2CO2CH3).
ethanol/water (3:1) to obtain 34% yield (m.p. 189–192°C, lit.
m.p. 190–192°C).
Spectroscopic characterization of 11-carbamoylundecanoic
acid. The mass spectrum of methyl 11-carbamoylundecanoate
is shown in Figure 5. The fragmentation pattern is that of a typ-
ical long-chain aliphatic molecule. A weak (M + 1) ion is ob-
served at m/z 244. Other diagnostic ions include: m/z 212 (M −
OCH3), 170 (M − CH2CO2CH3), and 59 (McLafferty-type re-
arrangement involving the carbamoyl group).
The IR spectrum showed two fairly sharp peaks at 3450 and
3220 cm−1 (N-H stretching bands). The O-H group stretching
exhibits characteristic absorption at the 3200–2500 cm−1 region.
There are two C=O peaks, at 1730 cm−1 due to the carboxylic
acid C=O and at 1650 cm−1 due to the amide C=O. Other char-
acteristic absorptions include N-H bending at 1600 cm−1 and C-
O stretching at 1460 cm−1. The 13C NMR (Fig. 6) indicated two
carbonyl carbon absorptions at 178.0 ppm (carbonyl carbon of
amide) and at 179.5 ppm (carbonyl carbon of carboxylic acid).
SCHEME 2
studies that have shown that boron trifluoride in acetic acid
would convert both syn- and anti-isomers to amide in excel-
lent yield (23). It is important to maintain the reaction tem-
perature between 110–115°C, because the product yield is
much reduced at reflux temperature, probably owing to other
side reactions that lead to polymer formation. Similarly, a
lower reaction temperature resulted in incomplete reaction.
For the Hofmann degradation, the 11-carbamoylunde-
canoic acid was transformed to the 11-(methoxycarbonyl-
amino)undecanoic acid (methyl carbamate) by treating a so-
lution of the amide in methanol with sodium methoxide and
bromine. Several attempts at direct conversion of the amide
to 11-aminoundecanoic acid by using concentrated sodium
hydroxide solution and bromine resulted in the hydrolysis of
the amide to give dodecanedioic acid in addition to some
methyl carbamate. The methyl carbamate (m.p. 84–86°C; ele-
mental analysis: calculated for C13H25NO4: C, 60.19; H, 9.73; FIG. 6. Proton-decoupled 13C nuclear magnetic resonance spectrum of
11-carbamoylundecanoic acid. Peaks are referenced to CH3OD at 49.0
N, 5.40; O, 24.68%. Found: C, 60.02; H, 9.81; N, 5.26; O,
24.91%) was obtained in 75% yield.
Hydrolysis of the methyl carbamate surprisingly required
prolonged refluxing for 17 h, to give a 53% yield of crude 11-
ppm. Sample was made to about 10 wt% in CD3OD. Operation fre-
quency at 76.6 MHz. Chemical shift (δ = ppm): carbonyl carbon of the
carboxylic acid 179.5 ppm, carbonyl carbon of the amide 178.0 ppm,
carbon alpha to the carboxylic acid 37.0 ppm, and carbon alpha to the
aminoundecanoic acid, which was recrystallized in 16 mL of amide 35 ppm.
JAOCS, Vol. 74, no. 5 (1997)

NYLON-12 AND NYLON-11 MONOMERS FROM VERNOLIC ACID
537
FIG. 9. Mass spectrum of methyl N,N-dimethylaminoundecanoate: m/z
243 (M + 1), m/z 44 [CH3NCH3]+, m/z 212 (M − OCH3), m/z 58
[(CH3)2NCH2]+, and m/z 156 (M − CH2CH2CO2CH3).
FIG. 7. Mass spectrum of methyl 11-(methoxycarbonylamino)unde-
canoate: m/z 88 base peak, m/z 242 (M − OCH3), m/z 214 (M − 59),
m/z 200 (M − 73), and m/z 144 [CH3O2CNH(CH2)5]+.
Spectroscopic characterization of 11-(methoxycarbony- uted to carbonyl carbon of the carboxylic acid) and the other
lamino)undecanoic acid. The mass spectral data of methyl at 157.12 ppm (assigned to the carbonyl carbon of the carba-
11-(methoxycarbonylamino)undecanoate are shown in Fig- mate). Other significant signals include the chemical shift at
ure 7. The base peak at m/z 88 is attributed to cleavage of the 55 ppm due to methyl carbon, at 42 ppm due to methylene
C10-C11 bond. Other prominent diagnostic ions include: m/z carbon alpha to the nitrogen, and at 35 ppm for methylene
242 (M − OCH3), 214 (M − carbomethoxy), and 144 carbon alpha to the carboxylic acid group.
[CH3O2CNH(CH2)5]+. The IR spectrum (cm−1) showed a
Spectroscopic characterization of 11-aminoundecanoic acid
broad OH absorption at 3500–2500, which overlaps with a (nylon-11 monomer). The gas chromatogram of the methylated
sharp absorption at 3370 due to the N-H stretching vibration. A sample of 11-aminoundecanoic acid showed two peaks. One peak
carbonyl absorption is shown at 1695, probably owing to over- corresponds to a primary amino ester H2N(CH2)10CO2CH3, and
lapping absorptions by the two carbonyl groups. C-N bending the second peak corresponds to the tertiary amino ester
vibration gave an absorption at 1515, while C-N stretching ap- (CH3)2N(CH2)10CO2CH3. Apparently, the amino group was
peared at 1240 and 1280, and C-O stretching was observed at methylated by diazomethane. Figure 8 shows the mass spectrum
1475.
of the primary amino ester with a protonated molecular ion (M +
The PNMR spectrum showed absorptions at 4.9 ppm 1) at m/z 216. Other fragmentation ions were m/z 184 (M −
(NH), 4.1 ppm (OCH3), 3.56 ppm (2H), 2.9 ppm (2H), 2.2 OCH3), m/z 142 (M − CH2CO2CH3) and m/z 30 (base peak). The
ppm (2H), 2.1 ppm (2H), 1.9 ppm (12H). The 13C NMR spec- mass spectral data of the tertiary amino ester (Fig. 9) gave a mol-
trum showed two carbonyl signals, one at 179.37 ppm (attrib- ecular ion (M+) peak at m/z 243. Other prominent fragmenta-
tions include: m/z 212 (M − 31), 58 [(CH3)2NCH2]+, 86
[(CH2)2NCH2CH2CH2]+, and 156 (M − CH2CH2CO2CH3).
The IR of 11-aminoundecanoic acid exhibited an asymmet-
rical N-H stretching absorption that appeared at 3400 cm−1,
while that of symmetrical N-H stretching was observed at 3200
cm−1. Almost overlapping these two bands was the strong OH
absorption at 3300–2500 cm−1. The C=O absorption was at
1640 cm−1. The -NH2 bending and C-N stretching were at 1540
and 1400 cm−1, respectively.
The potential commercial application of the syntheses out-
lined in these studies is enhanced by the fact that VO, the
source of vernolic acid, is a renewable raw material. These
studies represent the first reported production of both nylon-
12 and nylon-11 monomers from a single source. Further-
more, the three-step reaction sequence from 12-oxodode-
canoic acid oxime to 11-aminoundecanoic acid consists of
relatively simple reactions, thus offering an advantage over
the current use of castor oil, in which several more steps are
involved, one of which is the energy-intensive pyrolysis reac-
FIG. 8. Mass spectrum of methyl 11-aminoundecanoate: m/z 216 (M +
1), m/z 30 (base peak, [CH2=NH2]+), m/z 184 (M − OCH3) and m/z 142
(M − CH2CO2CH3).
JAOCS, Vol. 74, no. 5 (1997)

538
F.O. AYORINDE ET AL.
12,13-dihydroxyoleic and Threo-12,13-dihydroxystearic Acids,
Chem. Ind.: 1134–1135 (1960).
tion. Additionally, the intermediate 11-carbamoylundecanoic
acid produced in the present investigation could be a poten-
tial source of dodecane-1,12-diamine, one of the monomers
of nylon-12,12.
9. Yoshida, Y., M. Asano, H. Sugishita, and M. Matsunishi, 12-
Aminododecanoic Acid, Japanese Patent 60,163,849 (1985).
10. Griehl, W., and D. Ruestem, Nylon-12 Preparation, Properties
and Applications, Ind. Eng. Chem. 62(3):16–22 (1970).
11. Carothers, Linear Condensation Polymers, U.S. Patent
2,071,253 (1935).
ACKNOWLEDGMENTS
12. Wilke, G., Mulheim/Ruhr: Synthesen in der Cyclododekan-
Reihe, Angew Chemie. 69:397–398 (1957).
This research was supported in part by funding from the Howard
University Graduate Research Fund and USAID (#DAN-5053-G-
00-0032-00). The authors thank Ronald G. Fenner, director, Depart-
ment of Specialist Services, Ministry of Agriculture and Rural Re-
settlement, Zimbabwe, through whom vernonia seed was made
available. We also extend our gratitude to Richard Dugger (Interna-
tional Exchange of Trade and Technology, Culver, IN) for supply-
ing the crude V. galamensis oil used in this project.
13. SNIA VISCOSA, ω-Amino Acids, German Patent 3,010,673
(1980).
14. Hawkins, E.G.E., 12-Aminododecanoic Acid, French Patent
1,574,471 (1969).
15. Tsyskovskii and Razumovskii, Preparation of Amino Acids,
U.S.S.R. Patent 215,229 (1968).
16. Matsumoto, I., Bacterial Conversion of Alkylamines to Alka-
noic Acids, Japanese Patent 60 58,083 (1985).
17. Durston, P.J., Production of 11-Carbamoylundecanoic Acid,
British Patent 1283 796 (1972).
18. Kataoka, M., and M. Ohno, Syntheses and the Beckmann Fis-
sion of Cyclic α-Hydroxyimino Ketones, Bull. Chem. Soc.
Japan 46:3474–3477 (1973).
19. Ayorinde, F.O., G. Osman, R.L. Shepard, and F.T. Powers, Syn-
thesis of Azelaic Acid and Suberic Acid from Vernonia gala-
mensis Oil, J. Am. Chem. Soc. 65:1774–1777 (1988).
20. Silverstein, R.M., G.C. Bassler, and T.C. Morrill, Spectrometric
Identification of Organic Compounds, 4th edn., John Wiley &
Sons, New York, 1981, p. 269.
REFERENCES
1. Krewson, C.F., Naturally Occurring Epoxy Oils, J. Am. Oil
Chem. Soc. 45:250–255 (1968).
2. Earle, F.R., Epoxy Oils from Plant Seeds, Ibid. 47:510–513
(1970).
3. Ayorinde, F.O., F.T. Powers, L.D. Street, R.L. Shepard, and
D.N. Tabi, Synthesis of Dodecanedioic Acid from Vernonia
galamensis Oil, Ibid. 66:690–692 (1989).
4. Gunstone, F.D., Fatty Acids. Part II. The Nature of the Oxy-
genated Acid Present in Vernonia anthelmintica Seed Oil, J.
Chem. Soc.: 1611–1616 (1954).
5. Bharucha, K.E., and F.D. Gunstone, Vegetable Oils. IV. New
Method of Determining the Component Acids of Oils Contain-
ing Epoxy Acids and/or Hydroxy Acids, J. Sci. Food Agric.
7:606–609 (1956).
21. March, J., Advanced Organic Chemistry, 3rd edn., John Wiley
& Sons, New York, 1985, pp. 784, 1045.
22. Leusink, A.J., T.G. Meerbreak, and J.G. Noltes, Beckmann Re-
arrangement of Aldoximes Catalyzed by Transition Metal Salts:
A
Dehydration–Hydration Reaction, Recl. Trav. Chim.
6. Chisholm, M.J., and C.Y. Hopkins, An Oxygenated Fatty Acid
from the Seed of Hibiscus, Canadian J. Chem. 35:358–364
(1957).
7. Smith, C.R., K.F. Kock, and I.A. Wolff, Isolation of Vernolic
Acid from Vernonia anthelmintica Oil, J. Am. Oil Chem. Soc.
36:219–220. (1959).
Pays–Bas 95:123–125 (1976).
23. Hoffenberg, D.S., and J. Hauser, Dehydration of Beckmann Re-
arrangement of Aldoximes with Boron Fluoride. Conversion of
Aldoximes to Corresponding Amides, J. Org. Chem.
20:1496–1500 (1955).
8. Chisholm, M.J., and C.Y. Hopkins, Optical Isomers of Threo-
[Received February 9, 1996; accepted February 4, 1997]
JAOCS, Vol. 74, no. 5 (1997)