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Melting point / freezing point

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Endpoint:
melting point/freezing point
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
test procedure in accordance with national standard methods with acceptable restrictions
Qualifier:
according to
Guideline:
other: ISO 3016
GLP compliance:
no
Type of method:
pour point
Specific details on test material used for the study:
- Name of test material (as cited in study report): Novares LA 300
- Molecular formula (if other than submission substance): not applicable
- Molecular weight (if other than submission substance): not applicable
- Lot/batch- no: 28166
- Composition of test material, percentage of components: α-methylstyrene oligomers (ranges, n = 9)
Trimethylphenylindan [CAS No. 3910-35-8] 7.5 - 13.5 % / 10.8
Diphenylmethylpenten-1 [CAS No. 6362-80-7] 9.5 - 12.4 % / 11.1
Diphenylmethylpenten-2 [CAS No. 6258-73-7] 15.1 - 17.0 % / 16.1
Total dimers (without OH): ~35 - ~41 % / ca. 38
Total trimers (without OH): ~14 - ~25 % / 21.6
Total higher oligomers: ~6 %
Cumylphenol: 9.6 - 14.0 % / 11.5
Dicumylphenol: 19.4 - 25.0 % / 22.4
- Stability under test conditions: no measured data; based on chemical structure assumed to be stable
- Storage condition of test material: room temperature, exclusion of light
Key result
Melting / freezing pt.:
-14 °C
Atm. press.:
1 013 hPa
Decomposition:
no
Sublimation:
no
Endpoint:
melting point/freezing point
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The source test material ‘Oligomerisation and alkylation reaction products of 2-phenylpropene and phenol (OAPP) [EC no. 700-960-7] consists of a complex mixture of numerous aryl-aromatic constituents some of them containing also a phenolic structural element. The constituents can basically be divided into groups corresponding to the presence of phenolic OH-groups as well as their level of oligomerisation (dimers, trimers).
The target substance ‘Naphtha (petroleum), steam-cracked, C8-10 aromatic hydrocarbon fraction, alkylated and oligomerised’ (NAF-AO) [EC no. 701-299-207] consists also of a complex mixture of numerous aryl-aromatic constituents but without phenolic substituents present. Its components can basically be divided into groups corresponding to their level of oligomerisation (dimers, trimers, tetramers).
Both substances have various constituents in common (non-phenolic dimers, trimers and tetramers / higher oligomers). Their nature and their composition are considered to be sufficiently similar that melting point / freezing point are comparable for both substances. Therefore, the source substance OAPP is suited as supporting substance for NAF-AO with regard to melting / freezing, and data resulting from the source substance can be used for characterising the melting / freezing behaviour of the target substance NAF-AO.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The source substance OAPP is a UVCP substance obtained in an acid catalysed oligomerisation / alkylation reaction of the starting materials 2-phenylpropene and phenol. In this process, aromatic and phenolic components react with each other resulting on the one hand in oligomerisation products of 2-phenylpropene (reaction of 2-phenylpropene molecules among themselves, aryl-aliphatic substances) and on the other hand in 2-phenylprop-2-yl substituted (methylstyrenated) phenols (reaction of 2-phenylpropene with phenol, aralkyl-substituted phenols, phenolic substances). Besides dimeric products also trimeric and oligomeric products can be formed. Aromatic rings within the products are connected by methyl-substituted alkenyl carbon-chains in case of the 2-phenylpropene oligomers and by a single bridging carbon atom substituted by two methyl groups in case of methylstyrenated phenols. Besides phenyl substituents, non-phenolic oligomers of OAPP can also include indane substituents.
Based on the degree of oligomerisation four to five basic groups of constituents are formed. Two or three groups contain purely aryl-aliphatic (non-phenolic) substances differing only in the degree of oligomerisation (dimers, trimers, and higher (n ≥ 4) oligomers). Two groups comprise the alkylation products of phenol (mono or di 2-phenylprop-2-yl (methylstyryl) substituted phenols; phenolic products). Non-phenolic constituents (aryl-aliphatic oligomers) amount together to about 45 to 80% of OAPP, while the phenolic components contribute about 20 to 50%.
OAPP is a viscous oily material with a low water solubility (between 1 and 3.5 mg/L depending on its composition).
Basically, there are two centres for metabolic transformation present in both component types. On the one hand, the aliphatic structure linking aromatic/phenolic rings and especially their methyl substituents can be metabolised by oxidative transformation finally leading to carboxylic acids and eventually to decarboxylation. The second major pathway for metabolism concerns the aromatic rings. Metabolism will result in hydroxylated species like phenols or quinones.
The target substance NAF-AO is a UVCB substance as well, also obtained in an acid catalysed alkylation and oligomerisation reaction of the starting material ‘Naphtha (petroleum), steam-cracked, C8-10 aromatic hydrocarbon fraction’. This material comprises predominantly styrene and indene derivatives. In the production process, oligomerisation products of C8-10 aromatic hydrocarbons are formed consisting of dimeric, trimeric, and oligomeric (n ≥ 4) products. The individual constituents are the same as are produced in the production process of OAPP. Due to the composition of the starting material, no phenolic but only aryl-aliphatic products are formed. These products consist of two, three, or more aromatic rings connected by methyl-substituted alkenyl carbon-chains (dimers, trimers, oligomers). The aromatic substituents include besides benzene also indane. Based on the degree of oligomerisation, constituents are combined into three different groups (dimers, trimers and higher oligomers). Depending on the type of technical product (Novares L 100, L 700, TL 10), composition with respect to different component groups will vary (dimers from ca. 20 to 70%, trimers from ca. 10 to 30%, higher oligomers from ca. 15 to 50%).
NAF-AO is a viscous oily material with a low water solubility (between 0.6 and 1.3 mg/L depending on its composition). Thus, water solubility is somewhat lower than the water solubility of OAPP. Values for water solubility obtained by (Q)SAR (US EPA EPI suite) for individual model constituents are lower (between 0.082 and 0.038 mg/L for dimers and between 0.011 and 0.027 mg/L for trimers) indicating that measured values may overestimate the real water solubility. Overall, the water solubility of NAF-AO is low to very low depending on the technical product and its composition (higher percentages of trimers and higher oligomers will reduce the water solubility).
Basically, metabolism of NAF-AO is likely to proceed at the same two centres as in OAPP resulting in similar metabolic transformation products. Aliphatic structures with their methyl substituents linking aromatic rings can be metabolised by oxidative transformation finally leading to carboxylic acids and eventually to decarboxylation. The second sites for metabolic transformation are the aromatic rings present in the substance. Metabolism will result in hydroxylated species like phenols or quinones. Thus metabolism at aromatic rings can lead to similar products that are already present in the phenolic fraction of OAPP.

3. ANALOGUE APPROACH JUSTIFICATION
Source and target substance are to an essential part composed of the same constituents (aryl-aliphatic substances). The source substance OAPP contains, in addition, phenolic components. These are assessed to increase to some extent intermolecular forces by hydrogen bonding, which would cause a reduction of the melting / freezing temperature. However, hydroxyl groups constitute only a small fraction of the methylstyrenated phenols. The increase of intermolecular forces caused by hydrogen bonding will therefore be moderate. It is estimated that the melting point of the source substance is, if at all, only slightly lower than the melting / freezing point of the target substance.
Overall, the melting / freezing temperature of the target substance will be of the same magnitude as the melting / freezing temperature measured for the source substance. When adopting the melting temperature of the source substance as melting point for the target substance, only a small error will be made.
Reason / purpose:
read-across source
Key result
Melting / freezing pt.:
-14 °C
Atm. press.:
1 013 hPa
Decomposition:
no
Sublimation:
no
Remarks on result:
other: the test result of the source substance is adopted for the target substance

Description of key information

Freezing properties of the substance ‘Naphtha (petroleum), steam-cracked, C8-10 aromatic hydrocarbon fraction, alkylated and oligomerised’ (NAF-AO) (see Chapter 1) are characterised by a pour point of -14 °C that has been determined in a test according to guideline ISO 3016 using the closely structure related test material ‘Oligomerisation and alkylation reaction products of 2-phenylpropene and phenol’ (OAPP).

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:
-14 °C

Additional information

No data on freezing properties of the substance NAF-AO is available. But a reliable test according to guideline ISO 3016 was conducted using the closely structure related substance OAPP to determine its pour point. The pour point was shown to be -14 °C, and no decomposition or sublimation was noted.

Based on the structural similarity of both substances, it can be assumed that NAF-AO will have a similar pour point.