Three vinylbenzyl chloride isomers enter electronic chemical supply chains under three different CAS numbers. They share the molecular formula C9H9Cl, and two of them share a molecular weight of 152.62. They are nevertheless not interchangeable in formulation, in membrane manufacturing, or in advanced packaging dielectric work.

The category they sit in is large and still expanding. Grand View Research estimated the global electronic chemicals and materials market at USD 78.5 billion in 2025, with Asia Pacific accounting for 66.6% of that revenue. SEMI reported semiconductor materials revenue of USD 73.2 billion in 2025. Monomers represent a small share of that spend but a disproportionate share of process risk, which is why isomer identity belongs in a purchase specification rather than in a product description.

What follows is a comparison framework rather than a price list. It fixes what can be stated from documented physical constants, separates measured values from predicted ones, and shows where a mixed-isomer grade is a legitimate commercial answer and where it is not.

One Product Name, Four CAS Numbers

In supplier quotations, "vinylbenzyl chloride" can legitimately mean any of four distinct products:

• 4-Vinylbenzyl chloride — CAS 1592-20-7, EINECS 216-471-2, also listed as 1-(chloromethyl)-4-ethenyl-benzene. Supplied as a colorless to pale yellow transparent liquid, clear yellow in appearance.
• 1-(chloromethyl)-2-vinylbenzene — CAS 22570-84-9, EINECS 245-092-5, also referenced as 2-vinylbenzyl chloride or 2-(chloromethyl)styrene. Supplied as a light yellow to colorless liquid.
• 1-(chloromethyl)-3-vinylbenzene — CAS 39833-65-3, EINECS 254-649-1, also referenced as 3-(chloromethyl)styrene or m-(chloromethyl)styrene. Supplied as a light yellow to colorless liquid with approximately 0.1% TBC stabilizer.
• Vinylbenzyl chloride (mixed) — CAS 30030-25-2, EINECS 250-005-9. A mixture of the 3- and 4-isomers containing 50–100 ppm tert-butylcatechol as inhibitor.

All four share the formula C9H9Cl. The numeral in each single-isomer name denotes the position of substitution on the benzene ring, and that position is what changes polymerization behaviour, copolymer compatibility and the isomer composition a downstream formulation actually receives.

The practical consequence for procurement is simple: a specification that names only "vinylbenzyl chloride" without a CAS number cannot be compared between suppliers, cannot be re-ordered reliably, and cannot be qualified against a formulation target. The CAS number is the first comparison field — before purity, before packaging, and before price.

The Isomer Comparison Table

The table below reproduces the documented constants for the four grades. Where a value is not stated in the reference data, the field is marked as not stated rather than estimated.

All four grades carry the same application note in the reference data: core monomers for synthesizing high-performance negative photoresist resins, including E-beam electron beam photoresist, and advanced packaging dielectric materials, as well as for manufacturing homogeneous ion-exchange membranes, ultra-pure water resins and chelating resins.

Reading the Property Basis: Measured, Predicted, Not Stated

The most common comparison error in isomer sourcing is treating every number on a technical sheet as though it had the same evidentiary weight. It does not.

For the 4-isomer, the boiling point of 229 °C and the density of 1.083 g/mL at 25 °C are literature values, alongside a vapour density of 5.3, a refractive index of n20/D 1.572 and a vapour pressure of 1 mm Hg at 56.1 °C. These are the numbers a distillation cut point or a mass-balance calculation can reasonably be built on.

For the 2-isomer, the boiling point of 223.4 ± 9.0 °C and the density of 1.066 ± 0.06 g/cm³ are predicted values with stated tolerance bands. They are useful for screening and for understanding relative behaviour, but the ± 9.0 °C band is wide enough that it should not be used as a design value on its own.

For the 3-isomer, the reference data provided here does not state a boiling point or a density. That is not a gap to be filled by inference. It is a verification item: if a process depends on a distillation range or a volumetric feed calculation for the 3-isomer, the supplier should be asked for measured values on an actual batch, not for a predicted estimate.

A buyer's framework therefore needs a third comparison column alongside "value": the basis of the value — measured, literature, predicted, or not stated.

Stabilizer Content, Storage and Handling

Stabilizer content is a specification line, not a footnote. It changes the composition of what is delivered and it changes how the material must be stored.

• The 3-isomer is documented at approximately 0.1% TBC stabilizer (tert-butylcatechol).
• The mixed 3-/4-isomer grade is documented at 50–100 ppm tert-butylcatechol as inhibitor.
• Storage temperatures differ: the 4-isomer is specified for 2–8 °C, while the mixed grade is specified for −20 °C.
• The 4-isomer is insoluble in water and only sparingly soluble in chloroform — a handling constraint that matters when a formulation step assumes aqueous-phase separation.

Two practical consequences follow. First, a stabilizer level expressed in percent versus parts per million is a meaningful difference in specification language; both should be stated on the certificate of analysis with the batch number. Second, a −20 °C storage requirement versus a 2–8 °C requirement is a different cold-chain and warehousing proposition, and it should be priced and planned as such before the order is placed.

The documented operating mode for this monomer family is batch reaction under inert-gas protection with closed-system feeding and handling, supported by inert-gas sealed reactors, anhydrous and oxygen-free feeding systems, and high-purity filtration in clean environments. For a buyer, that translates into a due-diligence question: which of these controls are in place on the actual production line that will supply the order.

Application Mapping: Photoresist Resins, Membranes and Advanced Packaging

The three single isomers and the mixed grade are all documented as core monomers for high-performance negative photoresist resins, including E-beam electron beam photoresist, and for advanced packaging dielectric materials. They are also documented for manufacturing homogeneous ion-exchange membranes, ultra-pure water resins and chelating resins.

Beyond that shared statement, the function-level notes differ in ways that are useful at the selection stage.

Negative photoresist and advanced packaging dielectrics

The 4-isomer is described as a dual functional monomer that is readily derivatized by chloride displacement, and as a component of photoresist polymers, ion exchange resins, cross-linkable fibres, coupling agents and electroconducting polymers, and a starter for copolymer preparations. For a formulation team working on a photoresist resin backbone, that combination — a polymerisable vinyl group plus a displaceable chloromethyl group — is the reason a single, defined isomer is preferred over an unspecified mixture: the displacement reaction is the route to the pendant functionality, and its yield depends on what is actually in the reactor.

Ion-exchange membranes and ultrapure water resins

Where the target is a homogeneous ion-exchange membrane, ultra-pure water resin or chelating resin, the specification idiom is consistency. The mixed grade is defined only as a 3- and 4-isomer mixture; the reference data does not declare a fixed isomer ratio for it. A buyer whose membrane specification assumes a fixed functional-group distribution has a documented reason to require either a declared single isomer or a supplier-agreed, batch-consistent ratio.

General copolymer and intermediate work

The mixed grade is documented as capable of forming a high molecular mass homopolymer, copolymerising with many other monomers, and serving as a comonomer in a variety of specialty plastics, with reactions possible on the chloromethyl group either before or after polymerisation. It is also documented for acrylic emulsion pressure-sensitive adhesive compositions and as an organic synthesis and pharmaceutical intermediate. These are legitimate, well-established uses where a fixed isomer ratio is not the governing requirement.

Adjacent materials in the same procurement package

VBC isomer decisions rarely sit alone. Where advanced packaging dielectrics are in scope, 4,4'-(4,4'-Isopropylidenediphenoxy)diphthalic Anhydride (BPADA, CAS 38103-06-9) is the key synthetic monomer for high-performance polyimide used in 5G high-frequency and high-speed flexible copper-clad laminate, OLED flexible substrates and aerospace lightweight composites. BPADA is moisture-sensitive: on contact with water it undergoes hydrolysis ring-opening to a diacid and loses polymerisation activity, so it must be stored dry and sealed, and polymerised under inert gas in anhydrous polar solvents such as NMP or DMAc. Where photo-masking resins are in scope, 5-Methyl-1H-benzotriazole (5M-BTA, CAS 136-85-6) is documented as a copper and copper alloy corrosion inhibitor and anti-fading agent in photomasking resins.

A Five-Step Buyer's Comparison Framework

The framework below converts the constants above into a repeatable evaluation sequence. It is intended to run before commercial negotiation, not after.

Step 1 — Fix identity by CAS number. Require 22570-84-9, 39833-65-3, 1592-20-7 or 30030-25-2 to appear on the enquiry, the quotation, the label and the COA. A quotation that names only "vinylbenzyl chloride" cannot be compared across suppliers.

Step 2 — Fix the basis of every property value. Mark each constant as measured, literature, or predicted. Treat the 2-isomer's 223.4 ± 9.0 °C boiling point and 1.066 ± 0.06 g/cm³ density as screening values. Request measured boiling point and density for the 3-isomer if the process requires them.

Step 3 — Fix stabilizer and storage clauses. State the stabilizer identity and level (for example, approximately 0.1% TBC for the 3-isomer; 50–100 ppm tert-butylcatechol for the mixed grade) and the required storage temperature (2–8 °C for the 4-isomer; −20 °C for the mixed grade).

Step 4 — Fix purity grade and metal-ion limit. Electronic grade means ppb-level metal ion control. Specifications can be customised per customer requirement, including metal impurity specifications expressed at levels such as <10 ppb for semiconductor materials. Industrial grade and high purity grade are separate options and should not be substituted silently.

Step 5 — Fix supply and verification terms. Confirm batch traceability coding, retained samples, COA format, MSDS language, and the availability of third-party re-inspection. Documented options in this supply chain include third-party test reports from SGS, BV or Intertek, and packaging ranging from 1 kg to tons.

Where a Mixed-Isomer Grade Fits — and Where It Does Not

A comparison framework is only credible if it states where the cheaper or more readily available option is the correct one.

The mixed grade (CAS 30030-25-2) is the right answer when the downstream process is tuned to a mixture: homopolymer and copolymer preparation, comonomer use in specialty plastics, acrylic emulsion pressure-sensitive adhesive compositions, and organic synthesis or pharmaceutical intermediate work. It is also a reasonable answer where a supplier and buyer have jointly agreed a batch-consistent isomer ratio and the process is designed around it.

It is not a substitute in three documented cases:

• It cannot replace the 2-isomer at all. The mixed grade is a 3- and 4-isomer mixture. An ortho-isomer requirement cannot be met by it.
• It carries no declared fixed ratio in the reference specification. Because it is defined as a mixture, a formulation that depends on a specific functional-group distribution needs either a declared single isomer or an explicitly agreed ratio — otherwise the incoming composition varies with the batch.
• Its logistics profile is different. Storage at −20 °C and a 50–100 ppm inhibitor level are not interchangeable with a 2–8 °C, higher-stabilizer single-isomer specification. A receiving site without sub-zero warehousing should treat this as a genuine constraint on isomer choice.

The second boundary is informational rather than chemical. As noted above, the 2-isomer constants available in this reference set are predicted rather than measured, and the 3-isomer set does not state a boiling point or density at all. A buyer who builds a specification on those fields alone is comparing materials on unequal evidence. The remedy is not to guess — it is to request measured data before the specification is frozen.

Market Trend Analysis: What the Published Figures Support

Three published data points give the demand context for these monomers.

• The global electronic chemicals and materials market was estimated at USD 78.5 billion in 2025, with Asia Pacific accounting for 66.6% of revenue (Grand View Research).
• Global semiconductor materials market revenue reached USD 73.2 billion in 2025 (SEMI).
• The electronic-grade photoresist market was estimated at USD 4.96 billion in 2024 (Grand View Research).

These figures should be read with a scope warning. Published estimates for the same category diverge: Fortune Business Insights estimated the electronic chemicals and materials market at USD 75.6 billion for 2025, while SEMI reported USD 67.5 billion of semiconductor materials revenue for 2024. The differences reflect what each source includes — substrates, ancillary chemicals such as developers and strippers, hardware-linked materials. Two conclusions follow.

First, the direction is not in dispute: photoresist, semiconductor materials and electronic chemicals demand remains substantial and concentrated in Asia-Pacific supply chains. Second, no single published market figure should be used as a supplier qualification argument. A market-size number describes a category; it says nothing about whether a specific supplier can hold a metal impurity specification across consecutive batches.

Supplier Capability: What the Framework Should Verify

Jumingchem, formally Jiangsu Juming Chemical Technology Co., Ltd., is a specialty chemical manufacturer established in 2017 and located in Jiangsu Province, China. The company integrates research, development, production, sales and service, and its product categories include 5-Methyl-1H-benzotriazole, BPADA, 4-Vinylbenzyl chloride, Vinylbenzyl chloride, 1-(chloromethyl)-2-vinylbenzene and 1-(chloromethyl)-3-vinylbenzene, with a stated annual production capacity of 60,000 tons.

For the isomer comparison described in this article, the relevant capability points are these:

• Isomer composition control. Documented options include pure para-isomer at ≥99% p-VBC, pure ortho-isomer at ≥98% o-VBC, pure meta-isomer at ≥98% m-VBC, and any custom mixture ratio of o/m/p isomers.
• Purity grade definition. Industrial grade, high purity grade and electronic grade with ppb-level metal ions are offered, with metal ion content controlled per customer specification (for example, Na, Fe, Cu).
• Purification and process technology. Advanced microchannel and continuous flow technology is used for challenging chemical processes, with ppb-level metal ion impurity purification capability for electronic grade products.
• Cleanroom production. Operations are conducted in ISO 6 GMP cleanrooms with control over metal ions, particles and environmental parameters, using low-extraction materials such as 316L VIM/VAR stainless steel and PFA/PVDF.
• Analytical control. ICP-MS, HPLC and GC detection systems support quality control under a 100% test policy and an ISO9001 quality management system.
• Scale flexibility. Production ranges from gram-level research quantities to hundred-ton industrial production, with a stated lead time of 7–30 days and a minimum order quantity of 1 kg.
• Customisation. Molecular structure and synthesis route design, purity grade customisation, and packaging customisation from 1 kg to tons. Liquid VBC grades are offered in 25 kg HDPE drums, 200 kg steel-plastic composite drums and 1000 L IBCs; solid BPADA and 5-Me-BTA in 25 kg fibre drums with PE liner, 25 kg kraft paper bags and 500 kg bulk bags, with temperature-controlled packaging for long-distance hot-climate shipping and UN-certified dangerous goods packaging on request.
• Documentation. COA with custom test items and format, MSDS in multiple languages, custom labels, pre-shipment sample confirmation, and batch traceability coding, with third-party reports available from SGS, BV or Intertek.

Documented supply programmes provide a useful reference point for what an electronic-grade qualification looks like in practice. In one recorded programme, ArF photoresist monomer was supplied at an annual volume of 5 tons with metal impurities below 10 ppb, meeting SEMI Grade 4 requirements, supporting the client's verification by a top-tier Korean wafer fab. In another, OLED intermediates and photoresist monomers were supplied at 8 tons per year with metal impurities below 20 ppb and particle control at ≤0.1 μm. These are supplier-documented outcomes, and the appropriate use of them is as a template for what to request: the same batch-level evidence, verified against your own specification.

Future Outlook

Three directions appear likely to shape VBC isomer sourcing over the next planning cycle.

Isomer ratio becomes a specification, not a purchasing shortcut. As photoresist and advanced packaging dielectrics continue to demand tighter functional-group control, the ability to supply a declared pure isomer or a fixed custom o/m/p ratio moves from a differentiator to a baseline expectation. Buyers should expect to state a ratio and to receive batch data against it.

Metal impurity specifications continue to narrow. Electronic grade already means ppb-level control; the documented capability to customise metal impurity specifications suggests that buyers will increasingly write specifications such as <10 ppb for specific elements rather than accepting a generic grade declaration. Particle control at ≤0.1 μm belongs in the same conversation.

Development-stage collaboration becomes part of procurement. Custom isomer ratio development, CDMO process development from laboratory route optimisation to industrial scale-up, and microchannel continuous flow process transfer are documented service models. For buyers, the implication is that supplier selection increasingly happens at the sample stage rather than at the first commercial order — and the comparison framework should therefore be applied to development partners, not only to bidders.

Frequently Asked Questions

What are the CAS numbers for the vinylbenzyl chloride isomers?

1-(chloromethyl)-2-vinylbenzene is CAS 22570-84-9 (EINECS 245-092-5); 1-(chloromethyl)-3-vinylbenzene is CAS 39833-65-3 (EINECS 254-649-1); 4-vinylbenzyl chloride is CAS 1592-20-7 (EINECS 216-471-2); and vinylbenzyl chloride as a 3-/4-isomer mixture is CAS 30030-25-2 (EINECS 250-005-9). All four share the molecular formula C9H9Cl.

Can a mixed-isomer grade replace a single isomer?

Not in every case. Vinylbenzyl chloride (CAS 30030-25-2) is defined as a mixture of the 3- and 4-isomers and does not contain the 2-isomer, so it cannot satisfy an ortho-isomer requirement. The reference specification also does not declare a fixed isomer ratio for the mixed grade, so applications that depend on a defined functional-group distribution require either a declared single isomer or an agreed, batch-consistent ratio.

Why does the 3-isomer list a TBC stabilizer content?

The 3-isomer is documented with approximately 0.1% TBC stabilizer, where TBC refers to tert-butylcatechol. The mixed 3-/4-isomer grade is documented with 50–100 ppm tert-butylcatechol as inhibitor. Stabilizer identity and concentration affect the delivered composition and should be stated per batch on the certificate of analysis, particularly where the specification is written in percent for one grade and in parts per million for another.

Which physical constants in the isomer comparison are measured and which are predicted?

The 4-isomer values are literature-based: boiling point 229 °C, density 1.083 g/mL at 25 °C, vapour density 5.3 (vs air), refractive index n20/D 1.572, and vapour pressure 1 mm Hg at 56.1 °C. The 2-isomer values are predicted, with stated tolerances: boiling point 223.4 ± 9.0 °C and density 1.066 ± 0.06 g/cm³. The reference data for the 3-isomer does not state a boiling point or density. Buyers should request measured values for any constant the process depends on.

What purity grade and metal-ion limit should be specified for electronic-grade vinylbenzyl chloride?

Electronic grade denotes ppb-level metal ion control rather than a single universal number. Specifications can be customised to the customer's requirement, including metal impurity specifications at levels such as <10 ppb for semiconductor materials, with testing supported by ICP-MS, HPLC and GC systems under a 100% test policy. Industrial grade and high purity grade are separate grades, and the grade should be named explicitly on the purchase specification.

How should vinylbenzyl chloride isomers be stored and handled?

Storage requirements differ by grade: the 4-isomer is specified for 2–8 °C, while the mixed 3-/4-isomer grade is specified for −20 °C. The 4-isomer is insoluble in water and only sparingly soluble in chloroform. The documented operating mode for this monomer family is batch reaction under inert-gas protection with closed-system feeding and handling, supported by inert-gas sealed reactors and anhydrous, oxygen-free feeding systems, with high-purity filtration in clean environments.

A downloadable catalogue covering the vinylbenzyl chloride isomer range, BPADA and 5-Methyl-1H-benzotriazole is available here: Jiangsu Juming catalogue (PDF).