Temperatures and enthalpies of solid-solid and melting transitions of the odd-numbered n-alkanes C21, C23, C25, C27, and C29

Article abstract of DOI:10.1021/je0003501

Very high purity samples of normal pentacosane and heptacosane are made by synthesis: the procedures for the C₂₅ and C₂₇ synthesis and the original conditions of their purification, particularly using the extraction by supercritical carbon dioxide, are described. Measurements of temperatures and enthalpies of the solid-solid transitions and of the melting transition were carried out by differential scanning calorimetry on the C₂₅ and C₂₇ synthetic samples and the odd-numbered homologous n-alkanes (from C₂₁ to C₂₉). The results show the importance of the effect of the impurities, particularly for the δ and γ crystal-crystal transition temperatures of C₂₅ and C₂₇. Several current data of the literature are also shown concerning the temperatures and the enthalpies of solid-solid and melting transitions of these five n-alkanes.

Full text of DOI:10.1021/je0003501

1114
J . Chem. Eng. Data 2001, 46, 1114-1122
Ar ticles
Tem p er a tu r es a n d En th a lp ies of Solid -Solid a n d Meltin g
Tr a n sition s of th e Od d -Nu m ber ed n -Alk a n es C21, C23, C25, C27, a n d C29
Vir gin ie Ch eva llier ,† Moh a m m ed Bou r ou k ba ,† Dom in iqu e P etitjea n ,† Da n ielle Ba r th ,†
P a u l Du p u is,‡ a n d Mich el Dir a n d *,†
Laboratoire de Thermodynamique des Se´parations, UPRES EA n° 2287, E.N.S.I.C.-I.N.P.L., 1, rue Grandville
BP 451, F-54001 Nancy Cedex, France, and Laboratoire de Chimie Physique Macromole´culaire, UMR CNRS n°
7568, E.N.S.I.C.-I.N.P.L., 1, rue Grandville BP 451, F-54001 Nancy Cedex, France
Very high purity samples of normal pentacosane and heptacosane are made by synthesis: the procedures
for the C25 and C27 synthesis and the original conditions of their purification, particularly using the
extraction by supercritical carbon dioxide, are described. Measurements of temperatures and enthalpies
of the solid-solid transitions and of the melting transition were carried out by differential scanning
calorimetry on the C25 and C27 synthetic samples and the odd-numbered homologous n-alkanes (from C21
to C29). The results show the importance of the effect of the impurities, particularly for the δ and γ crystal-
crystal transition temperatures of C25 and C27. Several current data of the literature are also shown
concerning the temperatures and the enthalpies of solid-solid and melting transitions of these five
n-alkanes.
In tr od u ction
Schaerer et al., 1955; Schmidt et al., 1941; Seyer et al.,
1944; Sirota et al., 1993; Snyder et al., 1981; Srivastava et
al., 1993; Strobl et al., 1974; Ungar, 1983; Verdonk, 1938).
The aim of this article is to determine the impurity effects
(Ghogomu et al., 1990) on the temperatures and the
enthalpies of solid-solid and solid-liquid transitions, using
commercial and synthetic pure Cn, and to point to several
thermodynamic literature data for the odd-numbered
Because of the importance of the n-paraffins in petro-
leum technology, numerous studies have been carried out
to determine the thermodynamic data of pure n-alkanes
(hereafter denoted by Cn) (Achour et al., 1981; Andon et
al., 1976; Atkinson et al., 1969; Barbillon et al., 1991;
Bonsor et al., 1997; Bosselet et al., 1983; Broadhurst, 1962;
Domalski et al., 1990; Domanska et al., 1999; Doucet et
al., 1981; Doucet et al., 1984; Dreisbach, 1959; Fredricks,
1986; Hasnoui et al., 1998; Heyding et al., 1990; Hoffman
et al., 1953; J in et al., 1991; J osefiak et al., 1977; Lourdin,
1991; Maroncelli et al., 1982; Mazee, 1948; Mazee, 1949;
Messerly et al., 1967; Parks et al., 1929; Parks et al., 1930;
Robles et al., 1998; Schaerer et al., 1955; Schmidt et al.,
1941; Seyer et al., 1944; Sirota et al., 1993; Snyder et al.,
1981; Ungar, 1983) and their binary mixtures (Achour et
al., 1981; Achour et al., 1992; Achour-Boudjema et al., 1996;
Bosselet et al., 1983; Doucet et al., 1984; Ghogomu et al.,
1997; J outi et al., 1996; Nouar et al., 1997; Oonk et al.,
1998; Robles et al., 1996; Sabour et al., 1995; Srivastava,
2000). The odd-numbered homologues C2p+1, which display
increasing polymorphism as the temperature increases,
occupy a large place in the literature (Achour et al., 1981;
Barbillon et al., 1991; Bonsor et al., 1997; Bosselet et al.,
1983; Broadhurst, 1962; Domalski et al., 1990; Domanska
et al., 1994; Doucet et al., 1981; Doucet et al., 1984;
Dreisbach, 1959; Ewen et al., 1974; Fredricks, 1986;
Hasnoui et al., 1998; Heyding et al., 1990; Hoffman et al.,
1953; J osefiak et al., 1977; Maroncelli et al., 1985; Mazee,
1948; Mazee, 1949; Mu¨ller, 1932; Nozaki et al., 1995; Parks
et al., 1929; Piesczek et al., 1974; Robles et al., 1998;
homologous series C21 to C29
.
Exp er im en ta l Section
Commercial C21, C23, C25, C27, and C29 were purchased
from Fluka (purity g 98% (GC)).
Gen er a l Descr iption of th e Sa m ple Syn th esis (C25
a n d C27). Azelaic acid, thionyl chloride, 1-bromooctane, and
1-bromononane, with a purity g 99%, were purchased from
Aldrich and used without purification. Zinc chloride was
obtained from Fluka (purity g 98%).
First Step of the Chemical Synthesis: Azelaoyl Chloride.
A mixture of 49.5 g of the diacid and 78 mL of thionyl
chloride was refluxed for 24 h at 80 °C. The excess of
thionyl chloride was removed by distillation under atmo-
spheric pressure. Distillation under reduced pressure (98
°C, 53.3 Pa) provides 57 g (molar yield: 96%) of pure
azelaoyl chloride.
The infrared spectrum exhibited a strong peak in the
carbonyl region, at 1799 cm-1, assigned to acid chloride.
Second Step of the Chemical Synthesis: 9,17-Penta-
cosanedione and 10,18-Heptacosanedione. The chemical
synthesis of the two alkanes was carried out simulta-
neously.
* Corresponding author.
(i) Grignard Reagents. 1-Bromooctane (35 mL) (or 1-bro-
mononane (41 mL)) and an excess of magnesium turnings
† Laboratoire de Thermodynamique des Se´parations
‡ Laboratoire de Chimie Physique Macromole´culaire.
10.1021/je0003501 CCC: $20.00 © 2001 American Chemical Society
Published on Web 07/10/2001

J ournal of Chemical and Engineering Data, Vol. 46, No. 5, 2001 1115
Ta ble 1. Tem p er a tu r es a n d En th a lp ies of Solid -Solid
Tr a n sition s a n d th e Meltin g of C21: Com p a r ison betw een
th e Liter a tu r e Da ta (Tr a n sition Tem p er a tu r es a n d
En th a lp ies) of C21 a n d th e Exp er im en ta l Va lu es (∆T )
(0.1 K, ∆(∆Ho-d ) ) (140 J ‚m ol-1, ∆(∆fu sH) ) (450
J ‚m ol-1) of Th is Wor k for C21
(5 g) were allowed to react in 130 mL of anhydrous ether
to give the Grignard reagents.
(ii) Diketones. Zinc chloride (21.6 g, 0.158 mol) was
weighed into a 250 mL three-necked round-bottomed flask.
The mouth of the flask was connected to a vacuum pump.
The system was evacuated and dried. The zinc chloride was
slowly fused to a clear melt. After the flask was cooled to
room temperature in a vacuum, the vacuum pump line was
removed and 70 mL of anhydrous ether was added. The
mixture in the closed system was stirred magnetically until
the fused zinc chloride had dissolved and the solution
became colorless. To this solution, the Grignard reagent
was added rapidly. A thick, gray paste was obtained with
strong refluxing. After 20 min of stirring, ether was
removed and 33 mL of anhydrous benzene was added to
the pasty mixture. Azelaoyl chloride (11 mL) in anhydrous
benzene (140 mL) was added to the organozinc reagent over
a period of 15 min. The solution was stirred and refluxed
for 3 h under nitrogen. The mixture (gray paste) was then
hydrolyzed with 2 M hydrochloric acid. The organic layer
was separated, a solid was recovered, and benzene was
removed on a rotary evaporator. The crude products were
washed with water, dried, and purified by recrystallization
from benzene. 9,17-Pentacosanedione was obtained in 60
mass % yield (mp 96 °C), and 10,18-heptacosanedione, in
56 mass % yield (mp 99 °C).
To-d
fusion Tfus
ref
% purity
99
K
K
Barbillon et al., 1991
Broadhurst et al., 1962
Doucet et al., 1981
Dreisbach, 1959
Heyding et al., 1990
Maroncelli et al., 1985a
Mazee, 1948/1949a
Schaerer et al., 1955a
Schmidt et al., 1941
Seyer et al., 1944
Sirota et al., 1993
this work
305.1
306.15
305.7
313.4
313.15
313.7
313.65
312.15
97
99
99.6
305.15
305.75
305.95
305.65
313.5
313.35
312.6
313.6
313.25
313.16
99.9
99
g98
303.95
303.99
F
∆Ho-d
∆
fusH
∆HTT
o-d
J ‚mol-1 J ‚mol-1 J ‚mol-1
Barbillon et al., 1991
Bonsor et al., 1997
Broadhurst et al., 1962
Dreisbach et al., 1959
Maroncelli et al., 1985a
Mazee et al., 1948/1949a
Schaerer et al., 1955a
this work
99
16 500
15 600
15 481
46 000
75 500
47 698
47 697
47 698
99.6
17 154
15 070
15 481
13 356
70 710
70 425
The diketones were characterized by infrared spectros-
copy (wave number corresponding with CdO linked to
CH2), thin-layer chromatography (one spot for each prod-
uct), and 13C NMR.
99.9
g98
47 698
45 208
a
Quoted in TRC Databases, 1998.
Third Step of the Chemical Synthesis: C25 and C27. 9,-
17-Pentacosane dione (10.6 g) (or 11.4 g of 10,18-hepta-
cosanedione), 25 mL of hydrazine monohydrate, 25 mL of
glacial acetic acid, and 305 mL of 1-octanol were refluxed
under stirring at 140-150 °C for 9 h. The water formed
and the excess of hydrazine were removed with a Dean-
Stark apparatus. A solution of sodium octanolate (11 g of
sodium in 120 mL of 1-octanol) was added to the hydrazone.
The mixture was then refluxed for 24 h. The oil bath
temperature was increased until 180 °C. The cold mixture
was neutralized with 4 M HCl. The organic phase was
evaporated to dryness in a vacuum (∼133 Pa). The residual
semisolid was crystallized from ethanol to give a white solid
which was not pure: the main impurities were unreduced
ketones and alcohols formed by reduction of carbonyl
groups. The purification was monitored by infrared spec-
troscopy: after several recrystallizations in dichloro-1,2-
ethane, the CdO band disappeared but weak OH bands
remained; TLC showed two weak impurity spots.
conditions whenever necessary. The results of the purifica-
tion by this method have already been described in the
literature (Gandolfo et al., 1999).
Mea su r em en ts. 1H and 13C NMR spectra were recorded
on a Bruker AC-200 P spectrometer in deuteriochloroform
solution. Chemical shifts were given in δ downfield from
TMS. The FTIR spectra were measured with a Nicolet 210
spectrometer.
Products were analyzed by gas chromatography on a
Carlo Erba GC 6000 equipped with a capillary column
(WCOT ULTI-METAL, 10 m, 0.53 mm). The FID temper-
ature was 330 °C, with on-column injection. The oven
temperature was held at 50 °C for 3 min; then a temper-
ature gradient was operated (10 K‚min-1), and finally an
isotherm was maintained at 300 °C. The samples were
diluted in 0.5 mL of n-C7, and 0.5 µL of solution was
injected.
The calorimetric measurements were performed using
a differential scanning calorimeter SETARAM DSC III of
the Tian Calvet type. The samples were initially melted
and cooled in the measuring crucible. The DSC analyses
were carried out with a heating rate of 0.5 K‚min-1 from
293.15 K to 338.15 K. These experimental conditions
allowed the measurements of the onset and final temper-
atures of a transformation: the temperatures were deter-
mined with an accuracy of (0.1 K, according to the method
of measurements established by Courchinoux et al. (1988).
The enthalpies were obtained from the surface area defined
by the peaks and using a linear baseline between the onset
and the end of the transformations with a relative accuracy
of 1%. The apparatus was calibrated with the help of the
thermodynamic data of alumina (Ditmars et al., 1982), of
pure water, and of pure toluene. Experimental data of the
commercial samples are in good agreement with the
literature data (Tables 1-5), and this agreement justifies
the experimental method used.
Final purification was achieved by column chromatog-
raphy on silica gel (eluent toluene): fractions with one spot
were collected together and vacuum-dried to eliminate the
solvent. Synthetic C25 and C27 were obtained: C25 yield 32
mass %, mp 53 °C; C27 yield 29 mass %, mp 59 °C.
Purification by Supercritical Carbon Dioxide Extraction.
The solid feed was introduced in the autoclave, with a
stainless steel frit at the outlet column (height, 30 cm;
internal diameter, 23 mm); then the autoclave was closed.
Carbon dioxide (P ) 5 MPa, T ) 20 °C) was cooled (T ) 5
°C), pumped (Pmax ) 25 MPa, CO2 flow rate(max) ) 3.5
kg‚h-1), and then heated to be a supercritical fluid or a
liquid. It flows through the thermostated extraction col-
umn. At the outlet column, the mixture CO2-solutes was
expanded through three valves and the components were
separated in cyclonic separators. Finally CO2 was vented
through a rotameter and a gasmeter. A characteristic of
the process is to withdraw the solutes in atmospheric

1116 J ournal of Chemical and Engineering Data, Vol. 46, No. 5, 2001
Ta ble 2. Tem p er a tu r es a n d En th a lp ies of Solid -Solid Tr a n sition s a n d th e Meltin g of C23: Com p a r ison betw een th e
Liter a tu r e Da ta a n d th e Exp er im en ta l Va lu es of Th is Wor k (∆T ) (0.1 K, ∆(∆Ho-d ) ) (200 J ‚m ol-1, ∆(∆fu sH) ) (500
J ‚m ol-1
)
Tδ
To-d
TRI
TRII
Tfus
ref
% purity
99
K
K
K
K
K
Barbillon et al., 1991
Broadhurst et al., 1962
Domalski et al., 1990
Dreisbach, 1959
313.5
313.15
320.8
321.15
319.5
320.75
319.95
320.15
Fredricks, 1986
99
99
99.6
313.15
311.15
313.6
313.75
313.65
Heyding et al., 1990
Maroncelli et al., 1985a
Mazee, 1948/1949a
Schaerer et al., 1955a
Seyer et al., 1944
Sirota et al., 1993
Hasnaoui et al., 1988
Ungar, 1983
320.5
320.65
320.6
99.6
99
99
99
99.3
g98
314.45
318
307.7
310.5
311.15
312.7
312.4
313.85
314
314.8
317.7
317.9
318.65
Robles et al., 1998
this work
320.3
320.91
∆HTT
F
∆Hδ
∆Ho-d
∆HRII
∆
fusH
o-d
ref
J ‚mol-1
J ‚mol-1
J ‚mol-1
J ‚mol-1
J ‚mol-1
Barbillon et al., 1991
Bonsor et al., 1997
Bosselet et al., 1983a
Broadhurst et al., 1962
Domalski et al., 1990
Fredricks, 1986
99
21 500
21 927
52 250
84 000
99
76 061
81 170
21 757
53 974
52 839
99
99.6
25 808
23 430
22 604
21 757
Maroncelli et al., 1985a
Mazee, 1948/1949a
Schaerer et al., 1955a
Ungar, 1983
99.6
99.3
320
320
320<
53 974
52 600
50 863
Robles et al., 1998
this work
320<
19 600
23 063
g98
in the o-d peak
a
Quoted in TRC Databases, 1998.
Cn Str u ctu r a l Beh a vior ver su s Tem p er a tu r e:
Liter a tu r e Resu lts
The monoclinic space group, Aa, of this third ordered phase
of “low temperatures” has been determined by Ewen et al.
(1974), Piesczek et al. (1974), and Strobl et al. (1974) and
called B(Aa).
(iii) Order T Disorder Transition. This transition, which
gives a major thermal effect (Figures 1 and 2), corresponds
to the appearance of the following disordered phases:
(a) orthorhombic â(Fmmm) (Ungar, 1983; Ungar et
Masic, 1985) for C21, C23, and C25. When the temperature
increases, the molecules of this â(Fmmm) phase are driven
by a movement of the “Rotator” type, denoted RI. Hereafter,
this order-disorder transition is denoted the o-d transi-
tion.
The crystalline structure of pure Cn was described by
Mu¨ller and Saville (1925), and Mu¨ller (1932) observed the
existence of a solid-solid transition by X-ray diffraction,
when the temperature increases, with the appearance of
disordered phases that present molecular movements of the
“Rotator” type. The crystallographic structures of “low
temperature” phases have been recently specified by Craig
et al. (1994) and Chevallier et al. (1999), who have
respectively clarified the space groups and the correlations
between the crystalline long c-parameter and the number
of carbon atoms of pure Cn, particularly concerning the odd-
numbered C2p+1 and their phase, denoted â0(Pbcm), whose
space group was determined by Smith (1953).
The structural behavior of pure odd-numbered C2p+1 (21
e 2p + 1 e 29), as a function of the temperature, has been
the subject of numerous publications in the literature,
leading to the following results (Doucet et al., 1984; Ewen
et al., 1974; Hasnoui et al., 1988; Maroncelli et al., 1982;
Maroncelli et al., 1985; Nozaki et al., 1995; Piesczek et al.,
1974; Robles et al., 1998; Sirota et al., 1993; Snyder et al.,
1981; Sirota et al., 1995; Srivastava et al., 1993; Strobl et
al., 1974; Ungar, 1983; Ungar et al., 1985):
(b) triclinic RIII (Doucet et al., 1984; Robles et al., 1998;
Sirota et al., 1993; Sirota et al., 1995; Srivastava et al.
1993) for C27 and C29
.
(iv) Last Solid-Solid Transition. J ust below the melting
point, the following phases appear:
(a) rhombohedral R-RII (R3hm) (Ungar, 1983; Ungar and
Masic, 1985) for C23 and C25
.
(b) monoclinic RIV (Doucet et al., 1984; Robles et al.,
1998; Sirota et al., 1993; Sirota et al., 1995; Srivastava et
al., 1993) for C27 and C29
.
In summary, the phase succession, when the tempera-
ture increases, is as shown in Scheme 1.
(i) δ-Transition. C23, C25, C27, and C29 undergo the
transition highlighted and called the δ-transition by Snyder
et al. (1981). According to Nozaki et al. (1995), this crystal
Resu lts
T crystal transition leads to the phase denoted â′ (Pbnm).
0
Figures 1-4 show the DSC curves obtained for C21, C23
,
(ii) γ-Transition. A second crystal T crystal transition
has been observed in C25, C27, and C29 by Piesczek et al.
(1974) and by Maroncelli et al. (1982), who denoted it
transition as γ. It corresponds to the appearance of a
monoclinic phase, called B by Piesczek et al. (1974), IV by
Maroncelli et al. (1982), and M* by Robles et al. (1998).
C25, C27, and C29. The two higher thermal peaks correspond
respectively to the order-disorder transition, denoted o-d
transition, and to the fusion:
(a) The δ-transition is not observed for C21 (Figure 1). It
appears for C23 just below the order-disorder transition

J ournal of Chemical and Engineering Data, Vol. 46, No. 5, 2001 1117
F igu r e 1. DSC curve of C21 with increasing temperature: observation of the o-d transition â(Pbcm) f â(Fmmm) (first peak) and of the
melting (second peak).
Sch em e 1
peak (Figure 2a); for C25, C27, and C29, the thermal effect
of the δ-transition is clearly separated from the o-d
transition thermal accident (Figure 2b-d).
(b) The γ-transition is highlighted in C27 and C29 (Figure
2c and d)
(c) The last solid-solid transition, whose enthalpy is very
low, is observed only in C23 (Figure 2a).
The experimental data of temperatures and enthalpies
of solid-solid and solid-liquid transitions are reported in
Tables 1-5, in which they are compared with the literature
data.
(Tables 3 and 4, Figures 3 and 4): in general the latter are
higher. More particularly, a significant variation is ob-
served for the δ-transition temperature, which is very
sensitive to the presence of impurities. The phenomenon
has already been highlighted by Sabour et al. (1995) and
by J outi et al. (1996), respectively, in the binary C23-C24
and C21-C23 diagrams. These authors note a very strong
decrease of the δ-transition temperature when the C24 or
C21 molar concentration increases from that of pure com-
mercial C23 (about 7 K/1% molar increase of C24 or C21),
and they attribute it to an increase in the disorder of the
crystallographic structure of C23, produced by the presence
of a small amount of another Cn (n < 23 or n > 23).
For the synthetic C25 and C27, the δ-transition temper-
atures are higher than the values of the literature and our
own measurements on the commercial samples (Tables 3
and 4, Figures 3 and 4). Moreover, the addition of 0.3%
molar of C23 into the synthetic C25 sample provokes a
Taking account of the purity problems, the thermody-
namic values of commercial samples are comparable with
those of the literature. Nevertheless, concerning the solid-
solid transition and melting temperatures of C25 and C27
,
differences appear between the literature values or our own
experimental results, determined from the commercial
samples, and those measured on the synthetic samples

1118 J ournal of Chemical and Engineering Data, Vol. 46, No. 5, 2001
F igu r e 2. DSC curves of C23 (2a), C25 (2b), C27 (2c), and C29 (2d).
F igu r e 3. Influence of the impurities in the pure C25 on the δ-transition (first peak) and o-d transition (second peak) temperatures: the
sample obtained by synthesis presents the higher solid-solid transition temperatures; when 0.3 molar % of C23 is added to the C25 synthetic
sample, these transition temperatures decrease, but they are higher than those of the commercial C25. The γ-transition is not detected in
the samples of high purity.
decrease in the δ-transition temperature of 0.6 K (Table
3, Figure 3).
3) (Table 3, Figures 2b and 3): either it is mixed with the
o-d transition peak or the monoclinic B(Aa) phase appears
in the C25 because of the impurities, and so it is not present
in the very pure C25. For the two C27 samples, the thermal
effect of the γ-transition is clearly separated from the o-d
transition peak (Figures 2c and 4); the γ-transition tem-
perature of the synthetic sample is higher by 0.8 Kelvin in
regard to that of the commercial C27 (Table 4, Figure 4).
The effect of impurities is also observed for the γ-transi-
tion temperatures. Concerning C25, Ungar (1983), Snyder
et al. (1981), and Robles et al. (1998) observed this
transition at a few tenths of Kelvin below the o-d transi-
tion (Table 3). Like other authors (Achour et al., 1981;
Barbillon et al., 1991; Bosselet et al., 1983; Broadhurst,
1962; Dreisbach, 1959; Fredricks, 1986; Heyding et al.,
1990; Maroncelli, 1985; Parks et al., 1929, 1930; Seyer,
1944; Sirota et al., 1993), we do not detect the γ-transition
for the three C25 samples studied here (commercial No. 1,
synthetic No. 2, and synthetic with 0.3% molar of C23 No.
According to these observations, it appears that
(a) the synthetic C25 and C27 present a higher purity than
the commercial products, currently used to determine
thermodynamic data, and

J ournal of Chemical and Engineering Data, Vol. 46, No. 5, 2001 1119
F igu r e 4. Influence of the impurities in C27. As in C25, the solid-solid transition temperatures (δ-transition, first peak; γ-transition,
second peak) increase as the purity increases.
Ta ble 3. Tem p er a tu r es a n d En th a lp ies of Solid -Solid Tr a n sition s a n d th e Meltin g of C25: Com p a r ison betw een th e
Liter a tu r e Da ta a n d th e Exp er im en ta l Va lu es of Th is Wor k (∆T ) (0.1 K, ∆(∆Ho-d ) ) (280 J ‚m ol-1, ∆(∆fu sH) ) (500
a
J ‚m ol-1
)
Tδ
Tγ
To-d
TRI
TRII
Tfus
ref
% purity
K
K
K
K
K
K
Barbillon et al., 1991
Bosselet et al., 1983b
Broadhurst et al., 1962
Domanska et al., 1999
Dreisbach, 19665/1969
Fredricks, 1986
Heyding et al., 1990
Maroncelli et al., 1985b
Parks et al., 1929b
Achour et al., 1998
Schaerer et al.,1955b
Seyer et al., 1944
Sirota et al., 1981
Ungar, 1983
99
99
320
326.7
326.25
326.7
327.20
326.85
325.85
325.15
319.85
320.15
319.45
98
99
99
99.6
319.25
318.15
319.9
319.41
320.15
326.45
326.05
326.65
326.5
99.8
99
99
320.15
321
322.05
321.3
326.5
311.7
310.3
310.5
311.9
314.9
314.3
319.4
319.9
319.4
Snyder et al., 1981
Robles et al., 1998
no. 1 this worka
99.1
g98
320
321.2
322.6
326.4
320.66
320.80
320.70
327.03
327.13
327.08
no. 2 this worka
no. 3 this worka
∆Hδ
∆Hγ
∆Ho-d
∆HRII
∆fusH
ref
J ‚mol-1
J ‚mol-1
J ‚mol-1
J ‚mol-1
J ‚mol-1
Barbillon et al., 1991
Bonsor et al., 1997
Bosselet et al., 1983b
Broadhurst et al., 1962
Dreisbach, 1959
99
99
26 500
26 352
25 235
25 941
56 750
56 605
57 739
57 738
56 519
Fredricks, 1986
99
99.6
28 186
28 451
27 343
26 066
28 400
Maroncelli et al., 1985b
Achour et al., 1998
Schaerer et al., 1955b
Snyder et al., 1981
Ungar, 1983
56 702
57 739
99.8
99
99
99.1
g98
350
350
250
350e
Sirota et al., 1993
Robles et al., 1998
no. 1 this worka
57 170
57 180
56 663
57 122
56 915
350e
281
289
350
23 600
27 445
27 630
27 502
no. 2 this worka
no. 3 this worka
277
a
b
No. 1, commercial sample; no. 2, synthetic sample; no. 3, synthetic sample with 0.3% of C23
.
Quoted in TRC Databases, 1998.

1120 J ournal of Chemical and Engineering Data, Vol. 46, No. 5, 2001
Ta ble 4. Tem p er a tu r es a n d En th a lp ies of Solid -Solid Tr a n sition s a n d th e Meltin g of C27: Com p a r ison betw een th e
Liter a tu r e Da ta a n d th e Exp er im en ta l Va lu es of Th is Wor k (∆T ) (0.1 K, ∆(∆Ho-d ) ) (280 J ‚m ol-1, ∆(∆fu sH) ) (620
a
J ‚m ol-1
)
Tδ
Tγ
To-d
TRIV
Tfus
ref
% purity
98
K
K
K
K
K
Broadhurst et al., 1962
Doucet et al., 1981
Domanska et al., 1999
Dreisbach, 1959
325.75
324.75
327.40
331.55
330.95
331.85
332.15
331.15
331.15
331.83
332.7
Fredricks, 1986
99
99
96
99
99
99.6
99
326.85
325.15
325.85
326.7
325.6
326.5
Heyding et al., 1990
Hoffman et al., 1953
J osfiak et al., 1977
Lourdin, 1991
320.15
319.5
318.5
320.8
300.25
331.6
Maroncelli et al., 1985b
Schaerer et al., 1955b
Seyer et al., 1944
Sirota et al., 1993
Snyder et al., 1981
Robles et al., 1998
Verdonk, 1938
309.8
326.15
331.15
332.3
328.55
327.9
99
99.1
g98
324.95
320.8
322.3
326.95
326.5
325.9
321.15
326.75
326.82
309.8
312.9
331.6
332.15
332.37
332.38
no. 1 this worka
315.24
317.25
323.64
324.44
no. 2 this worka
∆Hδ
∆Hγ
∆Ho-d
∆fusH
ref
J ‚mol-1
J ‚mol-1
J ‚mol-1
J ‚mol-1
Broadhurst et al., 1962
Dreisbach, 1959
Fredricks, 1986
60417
60420
63086
59000
99
99
99.6
99
99.1
31384
26300
27196
26568
27100
19646
27778
27407
Lourdin, 1991
2200
2427
2385
2470
Maroncelli et al., 1985b
Schaerer et al., 1955b
Robles et al., 1998
Verdonk, 1938
293
270
60417
62800
58102
61697
62024
no. 1 this worka
g98
283
246
2523
2531
no. 2 this worka
a
b
No. 1, commercial sample; no. 2, synthetic sample. Quoted in TRC Databases, 1998.
Ta ble 5. Tem p er a tu r es a n d En th a lp ies of Solid -Solid Tr a n sition s a n d th e Meltin g of C29: Com p a r ison betw een th e
Liter a tu r e Da ta a n d th e Exp er im en ta l Va lu es of Th is Wor k (∆T ) (0.1 K, ∆(∆Ho-d ) ) (300 J ‚m ol-1, ∆(∆fu sH) ) (670
J ‚m ol-1
)
Tδ
Tγ
To-d
Tfus
ref
% purity
K
K
K
K
Broadhurst et al., 1962
Doucet et al., 1981
Dreisbach, 1959
Heyding et al., 1990
Maroncelli et al., 1985a
Schaerer et al., 1955a
Seyer et al., 1944
Sirota et al., 1993
this work
99
99.6
99.5
330.95
329.05
336.15
333.65
336.85
335.15
330.15
331.1
331.35
330.25
330.75
331.77
99
>99.5
310.2
322.4
336.55
336.5
336.55
336.8
g99.5
314.17
325.41
∆Hδ
∆Hγ
∆Ho-d
∆fusH
ref
J ‚mol-1
J ‚mol-1
J ‚mol-1
J ‚mol-1
Bonsor et al., 1997
Broadhurst, 1962
Maroncelli et al., 1985a
Schaerer et al., 1955a
this work
31 766
31 547
30 125
29 706
30 026
66 107
99.6
99.5
g99.5
293
248
2594
2468
66 107
66 939
a
Quoted in TRC Databases, 1998.
(b) the monoclinic B(Aa) phase stability is more sensitive
been highlighted for the δ- and γ-transition temperatures
which increase with the purity of the samples: the δ-transi-
tion, that is not present for C21, tends to merge with the
order-disorder o-d transition for C23 and disappears when
its purity increases. The same behavior occurs for the
γ-transition in C25, which is not observed in the synthetic
samples. The Cn chain length has an influence on the
existence of these solid-solid transitions, as do the impuri-
to impurities in C25 than in C27, as is the â′ (Pbnm) phase
0
stability in C23 with regard to that of C25
.
Con clu sion
We make use of a new procedure of Cn synthesis and
purification that leads to C25 and C27 of very high purity.
From these samples, the impurity effects have particularly

J ournal of Chemical and Engineering Data, Vol. 46, No. 5, 2001 1121
diagrams by differential scanning calorimetry. Thermochim. Acta
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1988, 128, 45-53.
γ-transition in C25. As it is very difficult to determine the
amount of impurities in these Cn by chromatographic
methods, the measurements of the temperatures of the δ-
or γ-transitions can give a relative evaluation of their state
of purity.
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We are indebted to Mr. Geoffrey Sockett, native speaker
of English and Professor of English at Ecole Nationale
Supe´rieure des Industries Chimiques for the correction of
this manuscript and to Luc Benoist, application Manager
at SETARAM Company, for the experiments of differential
thermal analysis.
Nom en cla tu r e
Tδ, ∆Hδ temperature and enthalpy of the δ-transition:
â0(Pbcm) f â′0(Pbnm)
Tγ, ∆Hγ temperature and enthalpy of the γ-transition:
â′0(Pbnm) f B(Aa)
To-d
∆Ho-d
TRI
,
temperature and enthalpy of the order-
disorder transition (o-d transition)
onset temperature of the Rotator phenomenon,
RI, observed in the â(Fmmm) disordered
phase.
TRII
∆HRII
,
temperature and enthalpy of the last solid-
solid transition for the C23 and C25
:
â(Fmmm) in RI f R-RII(R3hm).
temperature and enthalpy of the melting
Tfus
,
∆
fusH
∆HTT
F
enthalpy variation from the order-disorder
transition temperature (To-d) to the melting
o-d
temperature (Tfus
)
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Received for review November 1, 2000. Accepted April 18, 2001.
J E0003501