Neodecanoic Acid Physical & Chemical Properties:
Full Technical Reference
Acid value · Molecular weight · Boiling & flash points · Density · Viscosity · Refractive index · Solubility
🔗 View Neodecanoic Acid Product Page📋 Table of Contents
- Quick Reference Data Card
- Molecular & Structural Properties
- Acid Value: The Critical QC Parameter
- Thermal Properties: Boiling, Flash & Melting Points
- Physical Properties: Density, Viscosity & Refractive Index
- Solubility & Partition Coefficient
- Spectroscopic Identity & pKa
- NDA vs INA vs IOA: Side-by-Side Property Comparison
- Incoming QC Testing Methods
- Frequently Asked Questions
⚡ 1. Quick Reference Data Card
🔬 Neodecanoic Acid - Key Properties at a Glance (CAS 26896-20-8)
🧬 2. Molecular & Structural Properties
| Molecular formula | C₁₀H₂₀O₂ |
| Molecular weight | 172.26 g/mol |
| CAS Number | 26896-20-8 |
| EC Number | 248-093-8 |
| Functional group | –COOH (carboxylic acid) |
| Degree of unsaturation | 1 (COOH only; fully saturated chain) |
| Chiral centres | None (quaternary α-C is achiral) |
Commercial neodecanoic acid is a mixture of neo-type C10 isomers, all sharing the defining feature of a quaternary α-carbon (C2 carbon bears four carbon substituents, zero hydrogens). The principal isomers found in commercial NDA include:
- 2,2-Dimethyloctanoic acid - symmetric gem-dimethyl at C2
- 2-Methyl-2-ethylheptanoic acid - methyl + ethyl at C2
- 2,2-Diethylhexanoic acid - symmetric gem-diethyl at C2
- 2-Methyl-2-propylpentanoic acid - methyl + propyl at C2
Exact isomer distribution varies by Koch reaction conditions and C9 olefin feedstock composition; this does not affect functional performance in metal soap applications.
| α-Carbon type | Quaternary (no α-H) |
| β-H available | None at α-C ✅ |
| Hydrolysis resistance | Maximum in C8–C10 family |
| Thermal decomposition | No E2 β-elimination |
| Crystal packing | Disrupted by neo branching |
| Stereocentre | None - no optical isomers |
🧪 3. Acid Value: The Critical QC Parameter
The acid value (AV) is the single most important physical property of neodecanoic acid from a commercial and technical standpoint. It determines stoichiometric batch calculations for metal soap synthesis, is the primary identity check distinguishing NDA from INA and IOA, and must be verified batch-by-batch because it can vary between suppliers and even between production runs from the same supplier.
⭐ Acid Value of Neodecanoic Acid vs Iso-Acid Family
AV = 56,100 ÷ MW (theoretical).
Longer chain → higher MW → fewer moles of –COOH per gram → lower AV.
NDA: 56100 ÷ 172.26 = 325.7 (theoretical; commercial range 320–330 reflects isomer distribution)
🔧 Metal Soap Synthesis: Stoichiometric Calculation (AV-Based)
For any metal M(OH)ₙ + n × NDA → M(NDA)ₙ + n × H₂O:
Mass of M(OH)ₙ required = Equivalents × (MW of M(OH)ₙ ÷ n)
NDA batch AV = 325 mg KOH/g; use 1000 g NDA
Eq NDA = 1000 × 325 ÷ 56,100 = 5.794 mmol
Co(OH)₂ MW = 92.95; n = 2 (divalent Co)
Co(OH)₂ needed = 5.794 × (92.95 ÷ 2) = 269 g
If IOA AV (385) is mistakenly used for NDA (325):
Error = (385 − 325) ÷ 325 = +18% overestimation of acid equivalents
→ Metal content in product will be ~15% lower than target
→ Always use the batch-specific NDA AV from the COA
🌡️ 4. Thermal Properties: Boiling, Flash & Melting Points
| Thermal Property | Value | Method / Conditions | Practical Significance |
|---|---|---|---|
| Boiling point | 250–270 °C | Atmospheric (760 mmHg); mixture boiling range | Higher than IOA (228 °C) and INA (250–260 °C); thermally stable at typical metal soap synthesis temperatures (80–150 °C); distillation requires vacuum |
| Flash point ⭐ | 120–140 °C (CC) | Pensky-Martens closed cup (ASTM D93); GHS Category 4 combustible | No fire risk at ambient temperature; risk exists in heated synthesis vessels approaching flash point; no ATEX requirements for cold storage; Class 8 DG transport designation (corrosive, not flammable) takes precedence |
| Auto-ignition temperature | ~350–380 °C | Estimated from similar neo acids | Well above synthesis and storage temperatures; not a practical ignition risk under normal operating conditions |
| Melting point | ≈ −20 °C | Commercial mixture; DSC or visual | Fully liquid at all practical storage and processing temperatures; neo branching prevents crystallisation; no heat tracing required for drums, IBCs, or pipelines at ambient temperature |
| Lower explosive limit (LEL) | ~0.7% v/v (est.) | Estimated from C10 carboxylic acid data | Relevant only if NDA vapour accumulates in confined heated spaces; effectively irrelevant at ambient temperature due to very low VP |
| Thermal decomposition onset | > 300 °C | TGA in inert atmosphere | NDA itself is thermally stable well above synthesis temperatures; metal neodecanoates are also notably thermally stable due to no β-H elimination pathway |
| Combustion products | CO₂, H₂O | Complete combustion | Clean combustion products; no halogen or sulphur; standard firefighting media (CO₂, dry powder, foam) appropriate |
✅ Flash point and transport class: Despite having a flash point above 60 °C (Category 4 combustible liquid, not a Class 3 flammable liquid), neodecanoic acid is classified as a Class 8 corrosive dangerous good for transport (IMDG/ADR) because it is an organic acid with corrosive properties. The DG classification is determined by the corrosive hazard, not flammability - a point that sometimes confuses logistics teams who see the non-flammable flash point and assume the material is not DG. For every NDA shipment, a Class 8 DGD is required regardless of flash point.
⚖️ 5. Physical Properties: Density, Viscosity & Refractive Index
| Density at 20 °C | 0.903–0.910 g/cm³ |
| Typical value | ~0.906 g/cm³ |
| Specific gravity vs water | 0.90–0.91 (less dense than water) |
| Test method | ASTM D1298 (hydrometer) |
| Mass per 200 L drum | ~178–183 kg net |
Density comparison: NDA (0.906) ≈ INA (0.900) ≈ IOA (0.905); not useful alone for identity discrimination - use acid value.
| Dynamic viscosity (25 °C) | ~10–15 mPa·s |
| Kinematic viscosity (25 °C) | ~11–17 cSt |
| Viscosity at 50 °C | ~5–8 mPa·s |
| Flow character | Newtonian; easily pumpable |
| vs IOA (25 °C) | NDA slightly more viscous (~8 mPa·s for IOA) |
Higher viscosity than IOA reflects the longer C10 chain. Still easily handled at ambient temperature without heating; slightly warm to 30–40 °C for improved wetting of metal oxides in drier synthesis.
| nD²⁰ (20 °C) | 1.432–1.440 |
| Test method | Abbe refractometer (20 °C) |
| vs INA nD²⁰ | 1.432–1.438 (overlap ⚠️) |
| vs IOA nD²⁰ | 1.424–1.430 (clearly different ✅) |
| Identity use | Distinguishes NDA/INA from IOA; use AV to separate NDA from INA |
⚠️ Note: NDA and INA refractive indices overlap - RI alone cannot reliably distinguish them. Combine RI with acid value for definitive identification.
💧 6. Solubility & Partition Coefficient
| Solubility Parameter | Value | Practical Significance |
|---|---|---|
| Water solubility (25 °C) | < 0.03 g/100 mL | Practically insoluble; floats on water; more hydrophobic than INA and IOA; no risk of water contamination affecting bulk storage quality; environmental spills float and spread on water surface |
| Log P (octanol/water) | ~3.8–4.1 | Higher log P than INA (~3.5) and IOA (~3.0); more hydrophobic C10 chain; excellent oil/resin solubility; metal neodecanoates stay dissolved in hydrocarbon base stocks and alkyd systems even at low temperatures |
| Solubility in mineral spirit | Fully miscible | NDA dissolves completely in all common solvent fractions (white spirit, Shellsol, naphtha); no solubility limit at practical concentrations; enables high-metal-content drier solutions |
| Solubility in alkyd resin | Fully miscible | Excellent compatibility with medium- and long-oil alkyd resins; metal neodecanoates dissolve directly in the resin without phase separation or turbidity |
| Solubility in water-based systems | Very limited (as free acid) | Free NDA has very low water compatibility; for use in waterborne systems, must be converted to water-compatible salt form (e.g., amine salt) or used as the metal salt in appropriate formulation |
| Hildebrand solubility parameter | ~17–18 MPa½ | Compatible with most hydrocarbon polymers (alkyd, polyurethane, polyester); less compatible with highly polar or water-based systems in free acid form |
🔬 7. Spectroscopic Identity & pKa
| –COOH O–H stretch | 2500–3300 cm⁻¹ (broad) |
| C=O stretch (acid) | 1705–1720 cm⁻¹ (strong) |
| C–H stretch (alkyl) | 2850–2960 cm⁻¹ (strong) |
| C–O stretch (acid) | 1210–1320 cm⁻¹ |
| No α-C–H absorptions | Confirmed - no signal at ~2950 cm⁻¹ (α-H) ✅ |
The absence of α-C–H absorption can be used spectroscopically to confirm the neo (quaternary α-C) structure; reference standards available from NIST.
| –COOH proton | ~11–12 ppm (broad; disappears with D₂O) |
| α-C proton | ABSENT (quaternary α-C) ✅ |
| β-CH₂ protons | ~1.4–1.7 ppm |
| Gem-alkyl (neo) groups | ~0.8–1.0 ppm (overlapping methyl/methylene) |
| ¹H NMR characteristic | No multiplet at 2.3–2.5 ppm (α-H); confirms neo structure |
| pKa (aqueous, 25 °C) | ~5.1–5.3 |
| vs IOA pKa | IOA ~4.85 (slightly stronger acid) |
| Reason for higher pKa | Bulky neo substituents donate electron density to COOH via hyperconjugation → reduces acidity |
| pH of 1% aqueous dispersion | ~3.5–4.5 (poorly soluble; heterogeneous) |
| Impact on metal salt synthesis | No practical impact; metal oxide/hydroxide neutralisation is complete under standard conditions |
| Miscellaneous Properties | Value | Notes |
|---|---|---|
| Vapour pressure (20 °C) | < 0.05 mmHg | Extremely low; effectively non-volatile at ambient temperature; inhalation risk only from heated vapour or mist in enclosed spaces |
| Colour (APHA) | ≤ 50 (standard); ≤ 20 (premium) | Colourless to pale yellow liquid; colour specification important for cobalt and bismuth drier synthesis where pale base acid gives lighter-coloured product solutions |
| Odour | Mild fatty/oily | Less pungent than lower-MW fatty acids; negligible odour at room temperature due to low VP; mild odour detected near heated samples above 80 °C |
| Surface tension (25 °C) | ~26–28 mN/m | Surface-active; relevant for wetting of metal oxide powders in drier synthesis; lower ST than IOA aids dispersion of metal hydroxide in synthesis |
| Saponification value | Equal to acid value ± 3 | For a pure acid with no ester impurities, SV = AV; significant deviation (>5) indicates ester content - relevant for glycidyl ester synthesis feedstock purity |
| Dielectric constant | ~2.5–3.5 (est.) | Low dielectric constant; non-polar solvent character; high compatibility with alkyds and hydrocarbon resins |
⚖️ 8. NDA vs INA vs IOA: Side-by-Side Property Comparison
| Property | NDA (C10 Neo) ⭐ | INA (C9 Iso) | IOA / 2-EHA (C8) |
|---|---|---|---|
| Molecular weight | 172.26 | 158.24 | 144.21 |
| Acid value (mg KOH/g) | 320–330 | 348–360 | 375–395 ⭐ |
| α-Carbon | Quaternary (neo) | β-Methyl | Tertiary |
| Boiling point (°C) | 250–270 | 250–260 | 228 |
| Melting point (°C) | ≈ −20 | −50 to −55 | −59 ⭐ |
| Flash point (°C, CC) | 120–140 | 115–135 | 113–130 |
| Density (g/cm³, 20°C) | 0.903–0.910 | 0.898–0.905 | 0.902–0.910 |
| Refractive index nD²⁰ | 1.432–1.440 | 1.432–1.438 ⚠️ | 1.424–1.430 ✅ |
| pKa (aqueous) | ~5.1–5.3 | ~4.90 | ~4.85 |
| log P | ~3.8–4.1 | ~3.5 | ~3.0 |
| Water solubility | < 0.03 g/100 mL | < 0.05 g/100 mL | ~0.1 g/100 mL |
| H361 reproductive toxicity | No ✅ | No ✅ | H361 ⚠️ |
| Best QC discriminant | Acid Value (NDA: 320–330 / INA: 348–360 / IOA: 375–395) - clearly separates all three acids ✅ | ||
🧪 9. Incoming QC Testing Methods
| Test | Standard Method | NDA Pass Range | Equipment | Time | Priority |
|---|---|---|---|---|---|
| Acid value ⭐ ⭐ ⭐ | ASTM D974; ISO 660 | 315–335 mg KOH/g | Auto-titrator or burette | 20–30 min | Mandatory - every batch ✅ |
| Colour (APHA) | ASTM D1209 | ≤ 50 (std); ≤ 20 (premium) | Colorimeter or visual | 10 min | Recommended - every batch |
| Water content | Karl Fischer (ASTM E1064) | ≤ 0.10% | KF titrator | 20 min | Recommended - every batch |
| Density | ASTM D1298 or densitometer | 0.903–0.910 g/cm³ | Hydrometer / densitometer | 5 min | Optional (with AV confirmation) |
| Refractive index ⭐ | Abbe refractometer (20 °C) | nD²⁰ = 1.432–1.440 | Abbe refractometer | 5 min | Useful to distinguish NDA from IOA; combine with AV to separate NDA from INA |
| GC identity | GC-FID (polar column) | C10 neo acid peaks ≥ 90% | GC-FID | 45–60 min | First order qualification; periodic audit |
| Iron content | ICP-OES | ≤ 5 ppm (premium) | ICP (outsource) | 1–3 days | For glycidyl ester synthesis and premium drier applications |
💡 Two-parameter rapid NDA identity check (30 minutes): (1) Acid value - should be 315–335 mg KOH/g. If result is 348–360 → likely INA; if 375–395 → likely IOA; if <310 → wrong product or diluted. (2) Refractive index - should be 1.432–1.440. If result is 1.424–1.430 → definitely IOA. Note: RI alone cannot separate NDA from INA (ranges overlap) - acid value is the definitive discriminant between NDA and INA. Together, the two tests in 30 minutes confirm NDA identity with high confidence.
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❓ 10. Frequently Asked Questions
Q1: What is the molecular weight of neodecanoic acid?
The molecular weight of neodecanoic acid is 172.26 g/mol, corresponding to the molecular formula C₁₀H₂₀O₂. This is the weight of a single molecule - the weight of all the atoms (10 carbons × 12 + 20 hydrogens × 1 + 2 oxygens × 16 = 172 g/mol). Since commercial neodecanoic acid is a mixture of neo-type C10 isomers, all with the same molecular formula C₁₀H₂₀O₂, the molecular weight of 172.26 g/mol applies to all isomers in the mixture. For comparison: isononanoic acid (INA, C9) has MW = 158.24 g/mol; isooctanoic acid (IOA, C8) has MW = 144.21 g/mol. NDA's higher MW is directly responsible for its lower acid value (~325 vs ~354 vs ~385 mg KOH/g) and means that per gram of acid, NDA delivers fewer moles of carboxylate than INA or IOA - an important consideration for metal soap synthesis stoichiometry.
Q2: What is the acid value of neodecanoic acid and why is it important?
The acid value (AV) of neodecanoic acid is approximately 320–330 mg KOH/g for commercial grades (theoretical value 325.7 mg KOH/g based on MW 172.26). The acid value measures how many milligrams of KOH are required to neutralise the free acid groups in one gram of sample - it is essentially a measure of the concentration of carboxylic acid groups. It is the single most important quality parameter for NDA because: (1) it determines the stoichiometric metal oxide charge in metal salt synthesis (error in AV → error in metal content of the product); (2) it is the primary identity test distinguishing NDA (AV 320–330) from INA (AV 348–360) and IOA (AV 375–395); and (3) it varies batch-to-batch from the same supplier depending on the exact isomer composition, so the actual batch AV from the COA must be used for synthesis calculations - never assume the same AV as a previous batch. Test method: ASTM D974 (potentiometric titration with KOH in isopropanol vs phenolphthalein indicator).
Q3: What is the boiling point of neodecanoic acid?
Neodecanoic acid boils in the range of approximately 250–270 °C at atmospheric pressure (760 mmHg). Since commercial NDA is a mixture of neo-type C10 isomers with slightly different boiling points, the boiling point is reported as a range rather than a single value. The boiling point is significantly above the typical synthesis and processing temperatures for metal soap production (80–150 °C), meaning NDA does not boil off or significantly evaporate during synthesis. The high boiling point (combined with the very low vapour pressure of <0.05 mmHg at 20 °C) also means NDA is effectively non-volatile at ambient temperature - inhalation exposure risk is negligible during cold handling operations. Vacuum distillation (50–80 mmHg) reduces the effective boiling point to approximately 150–180 °C, which is relevant for purification of NDA or its derivatives.
Q4: What is the flash point of neodecanoic acid and what are its transport implications?
The flash point of neodecanoic acid is approximately 120–140 °C (closed cup), which places it in GHS Category 4 (Combustible liquid - H227). This means NDA does not pose a significant fire risk at room temperature (unlike Class 3 flammable liquids with flash points below 60 °C). However, the flash point does not determine the transport classification: NDA is classified as a Class 8 Dangerous Good (Corrosive liquid) under IMDG, ADR, and IATA, with UN number 3265 and Packing Group III. This is because organic carboxylic acids with corrosive potential are classified based on their acidic/corrosive properties, not their flammability. Even though NDA is not a flammable liquid at ambient temperature, every sea shipment requires a Class 8 Dangerous Goods Declaration (DGD), UN-certified packaging, and a Container Packing Certificate. Logistics teams who see the high flash point and assume no DG declaration is needed are making a critical error - always consult the supplier's SDS and verify DG classification before booking freight.
Q5: What is the density of neodecanoic acid and how many kg are in a 200 L drum?
The density of neodecanoic acid at 20 °C is approximately 0.903–0.910 g/cm³, with a typical value of ~0.906 g/cm³. This means NDA is slightly less dense than water (0.998 g/cm³) and will float on water. For a standard 200 L steel drum, the net weight of NDA is approximately 178–183 kg (200 L × 0.906 kg/L − allowance for headspace and not completely filled). For an IBC (1,000 L), the net weight is approximately 890–910 kg. For an ISO tank (~20,000 L capacity), the net weight is approximately 18,000–18,200 kg (18 MT). These figures are approximate - always use the density from the batch COA for precise mass calculations. The density of NDA is very similar to IOA and INA, making density alone insufficient for product identity discrimination. Use acid value as the primary identity test.
Q6: How do I distinguish neodecanoic acid from isononanoic acid by laboratory testing?
The definitive laboratory test to distinguish neodecanoic acid from isononanoic acid is acid value titration: NDA has AV ~320–330 mg KOH/g; INA has AV ~348–360 mg KOH/g. A difference of ~25–30 mg KOH/g between the two is easily measured by standard potentiometric or indicator titration and clearly discriminates the two products. The refractive index (NDA: ~1.432–1.440; INA: ~1.432–1.438) is not reliable alone because the ranges overlap - RI is only useful to distinguish NDA/INA from IOA (IOA RI = 1.424–1.430, clearly lower). For a definitive identity confirmation, especially on a first order from a new supplier, GC-FID analysis can confirm the C10 neo acid carbon chain distribution and distinguish NDA from INA by their chromatographic profiles. A rapid practical protocol: titrate acid value (30 min) - if AV is 315–335 → confirmed NDA; if 345–365 → suspected INA, confirm with GC.
Request COA & Technical Data for Neodecanoic Acid
Contact Sinolook Chemical
Neodecanoic acid CAS 26896-20-8 · AV 315–335 mg KOH/g · APHA ≤50 (std) / ≤20 (premium)
No H361 ✅ · REACH OR for EU · Full COA per batch · DG Class 8 export documentation
