3,5-Dimethoxybenzyl Alcohol: Properties, Handling & Lab Use

3,5-Dimethoxybenzyl alcohol is an aromatic primary alcohol bearing two methoxy substituents at the 3- and 5-positions of the benzene ring, widely used as a versatile building block and protecting-group precursor in organic synthesis.

CAS Number

33528-00-6

Molecular Formula

C₉H₁₂O₃

Molecular Weight

168.19 g/mol

Appearance

White to off-white crystalline solid

Functional Group

Primary benzylic alcohol with two methoxy groups

Solubility

Soluble in common organic solvents (e.g., ethanol, DCM, ethyl acetate); low solubility in water

Storage Conditions

Store in a cool, dry, well-ventilated area, away from light and moisture

Chemical Identity and Physical Properties

3,5-Dimethoxybenzyl alcohol (CAS 33528-00-6; Aladdin SKU D123146) is an aromatic primary alcohol with the molecular formula C₉H₁₂O₃ and a molecular weight of 168.19 g/mol. The compound features a benzene ring symmetrically substituted with methoxy groups at the 3- and 5-positions and a hydroxymethyl (–CH₂OH) group at the 1-position.

The molecule typically appears as a white to off-white crystalline solid at ambient temperature. It is soluble in polar aprotic and protic organic solvents such as dichloromethane, ethyl acetate, tetrahydrofuran, and ethanol, but exhibits low aqueous solubility. The electron-donating methoxy substituents impart increased electron density to the aromatic ring, influencing both the reactivity of the benzylic alcohol and the ring's behavior toward electrophilic aromatic substitution reactions.

Key Laboratory Applications

3,5-Dimethoxybenzyl alcohol serves as a valuable building block across several domains of synthetic organic chemistry:

• Protecting group precursor: The benzylic alcohol can be converted to the corresponding chloride, bromide, or carbonate to generate 3,5-dimethoxybenzyl-type protecting groups for amines, carboxylic acids, and alcohols. These groups are notable for their selective removal under mild acidic or hydrogenolytic conditions.
• Intermediate in natural product and pharmaceutical synthesis: The 3,5-dimethoxybenzyl motif appears in various biologically active molecules; this alcohol serves as a convenient entry point for constructing such scaffolds.
• Resin and polymer functionalization: Dimethoxybenzyl alcohol derivatives have been applied in solid-phase synthesis as linker precursors, exploiting the acid-labile character of electron-rich benzylic linkages.
• Oxidation substrate: Controlled oxidation of the primary alcohol yields 3,5-dimethoxybenzaldehyde, enabling access to aldehyde-based synthetic pathways.
• Cross-coupling partner: After activation (e.g., mesylation or tosylation), the compound can serve as an electrophile in metal-catalysed coupling reactions.

Safe Handling and Storage Guidelines

While 3,5-Dimethoxybenzyl alcohol is not classified as an acutely highly hazardous substance, standard laboratory precautions for organic reagents must be observed:

• Personal protective equipment: Wear appropriate chemical-resistant gloves, safety glasses or goggles, and a laboratory coat during weighing and handling. If fine dust is generated, use a dust mask or work in a fume hood.
• Ventilation: Handle in a well-ventilated laboratory or fume hood to minimise inhalation exposure.
• Storage: Store in a tightly sealed container in a cool (below 25 °C), dry, and well-ventilated area, protected from light and moisture. Keep away from strong oxidising agents and strong acids.
• Spill management: Contain spills with inert absorbent material (e.g., vermiculite or dry sand) and dispose of according to local regulations for organic chemical waste.
• First aid: In case of skin or eye contact, rinse thoroughly with water. Seek medical advice if irritation persists. Consult the Safety Data Sheet (SDS) for complete hazard information before use.

Always consult the current SDS provided by Aladdin Scientific before working with this compound.

Recommended Handling Protocols for Common Reactions

The following general protocols outline best practices when using 3,5-Dimethoxybenzyl alcohol as a synthetic reagent:

Activation to the Benzyl Halide

1. Dissolve 3,5-Dimethoxybenzyl alcohol in anhydrous dichloromethane or diethyl ether under an inert atmosphere (N₂ or Ar).
2. Cool the solution to 0 °C and add thionyl chloride (1.1 equiv) or phosphorus tribromide (0.35 equiv for the bromide) dropwise.
3. Allow the reaction to warm to room temperature and stir until TLC indicates complete conversion.
4. Quench carefully with saturated aqueous sodium bicarbonate, extract, dry over anhydrous MgSO₄, and concentrate under reduced pressure.
5. Use the resulting halide promptly, as benzylic halides can be moisture-sensitive and prone to hydrolysis.

Oxidation to 3,5-Dimethoxybenzaldehyde

1. Dissolve the alcohol in DCM and add Dess-Martin periodinane (1.1–1.2 equiv) or Swern oxidation reagents under standard conditions.
2. Monitor by TLC; upon completion, quench and work up according to the chosen oxidant's standard procedure.
3. Purify by flash chromatography (silica gel, hexane/ethyl acetate gradient).

Note: All reactions involving moisture-sensitive intermediates or exothermic reagents (e.g., SOCl₂, oxalyl chloride) must be conducted in adequately sized, dry glassware under an inert atmosphere, with appropriate temperature control.

Quality, Purity and Procurement Guidance

For reproducible experimental results, reagent quality is critical. When sourcing 3,5-Dimethoxybenzyl alcohol (Aladdin SKU: D123146), consider the following:

• Purity specification: Confirm the purity grade meets your application's requirements. For sensitive synthetic steps, reagents of ≥97% purity (GC or HPLC assay) are recommended. Verify the certificate of analysis (CoA) for lot-specific data.
• Identity confirmation: Cross-check the CAS number (33528-00-6) and confirm structure by ¹H NMR (characteristic aromatic proton pattern for 1,3,5-trisubstituted ring) and IR spectroscopy before use in critical applications.
• Packaging and quantity: Select appropriate pack sizes to minimise repeated opening of containers, which can introduce moisture and reduce shelf life. Re-seal under inert gas (N₂ or Ar) if long-term storage is needed.
• Regulatory and documentation: Request the current SDS, CoA, and any relevant export/import documentation from Aladdin Scientific at the time of procurement.

Frequently asked questions

What is 3,5-Dimethoxybenzyl alcohol used for in organic synthesis?

3,5-Dimethoxybenzyl alcohol is primarily used as a synthetic building block and protecting-group precursor. It can be converted to benzylic halides or carbonates for amine, alcohol, or acid protection, and can be oxidised to the corresponding aldehyde for further elaboration. The electron-rich aromatic ring also makes it useful as a linker precursor in solid-phase synthesis.

How should 3,5-Dimethoxybenzyl alcohol be stored to maintain its quality?

Store 3,5-Dimethoxybenzyl alcohol in a tightly sealed container in a cool (below 25 °C), dry, and well-ventilated area, away from direct light, moisture, and strong oxidising agents. For long-term storage, re-seal under an inert atmosphere (N₂ or Ar) after each use to prevent moisture uptake and potential oxidation.

What solvents are suitable for dissolving 3,5-Dimethoxybenzyl alcohol?

3,5-Dimethoxybenzyl alcohol dissolves readily in common organic solvents including dichloromethane, ethyl acetate, tetrahydrofuran, and ethanol. Its aqueous solubility is low, making it best suited for reactions conducted in organic solvent systems.

How do I confirm the identity and purity of 3,5-Dimethoxybenzyl alcohol upon receipt?

Confirm identity by checking the CAS number (33528-00-6) on the label and reviewing the Certificate of Analysis (CoA) for the specific lot. Structural confirmation can be performed by ¹H NMR, which should show characteristic signals for the 1,3,5-trisubstituted aromatic ring, the methoxy groups, and the benzylic CH₂ protons. Purity is typically assessed by GC or HPLC as stated on the CoA.

Is 3,5-Dimethoxybenzyl alcohol available from Aladdin Scientific, and what is the SKU?

Yes, 3,5-Dimethoxybenzyl alcohol is available from Aladdin Scientific under SKU D123146. Contact Aladdin Scientific or visit the product page for current pricing, available pack sizes, and lead times.

References

1. March, J. Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, 4th ed.; Wiley-Interscience: New York, 1992. (General reference for benzylic alcohol reactivity and protecting group chemistry.)
2. Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic Synthesis, 4th ed.; Wiley: Hoboken, NJ, 2007. (Reference for dimethoxybenzyl protecting groups and their cleavage conditions.)
3. Aladdin Scientific. Product page for 3,5-Dimethoxybenzyl alcohol, SKU D123146. (Accessed via Aladdin Scientific website; consult for current CoA and SDS.)

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