9-Bromo-1-nonanol: Synthesis, Handling & Application Protocol

9-Bromo-1-nonanol is a bifunctional C9 alkyl reagent bearing a terminal bromine electrophile and a primary hydroxyl nucleophile, making it a versatile building block for organic synthesis, surface functionalization, and polymer chemistry.

CAS Number

13688-95-4

Molecular Formula

C9H19BrO

Molecular Weight

223.15 g/mol

Functional Groups

Primary alkyl bromide (C9) and primary alcohol

Key Applications

Organic synthesis, SAM formation, bifunctional linker, surface modification

Storage Conditions

Cool, dry, well-ventilated area; away from light and moisture

Overview and Chemical Properties

9-Bromo-1-nonanol (CAS 13688-95-4; Aladdin SKU B124493) is a linear nine-carbon bifunctional molecule with a primary alkyl bromide at the ω-terminus and a primary hydroxyl group at the α-terminus. Its molecular formula is C₉H₁₉BrO and its molecular weight is approximately 223.15 g/mol.

The two orthogonal reactive handles allow selective transformations: the C–Br bond is susceptible to nucleophilic substitution (S_N2), elimination (E2), metal-halogen exchange, and radical reactions, while the –OH group can be esterified, etherified, oxidized, or protected with standard hydroxyl-protecting groups (e.g., TBS, THP, Bn). This orthogonality makes 9-Bromo-1-nonanol an attractive building block in multi-step synthesis and surface-chemistry workflows.

The compound is a colorless to pale-yellow liquid or low-melting solid at room temperature. It is miscible with common organic solvents such as dichloromethane, THF, ethyl acetate, and DMF, and is practically insoluble in water.

Safety and Handling

Personal Protective Equipment: Always wear nitrile gloves, a laboratory coat, and safety goggles when handling 9-Bromo-1-nonanol. Work in a well-ventilated fume hood to prevent inhalation of vapors.

Hazard Summary: As an alkyl bromide and an alcohol, this compound is a potential irritant to skin, eyes, and respiratory mucosa. Consult the Safety Data Sheet (SDS) before use. The compound is not classified as acutely toxic by standard routes at typical laboratory exposure levels, but chronic exposure should be minimized following good laboratory practice.

Storage: Store in a tightly sealed container in a cool (2–8 °C recommended for long-term stability), dry, and well-ventilated location away from direct light, ignition sources, and oxidizing agents. Under proper storage, the compound is stable for extended periods.

Waste Disposal: Dispose of waste solvent and unused reagent in accordance with local institutional and governmental regulations for halogenated organic waste. Do not pour down the drain.

Step-by-Step Protocol: Using 9-Bromo-1-nonanol as a Bifunctional Linker

The following general protocol describes selective alkylation at the bromide terminus while preserving the hydroxyl group, a common strategy for chain-elongation and macrocycle synthesis.

1. Reagent preparation: Weigh the required amount of 9-Bromo-1-nonanol (B124493) in the fume hood. If the hydroxyl group must be protected, treat with an appropriate protecting group reagent (e.g., TBSCl, imidazole, DMF, 0 °C → RT, 2 h) before proceeding to the alkylation step.
2. Nucleophile preparation: Dissolve the nucleophilic partner (e.g., a thiol, amine, malonate, or organometallic species) in anhydrous solvent (DMF, THF, or acetonitrile) under inert atmosphere (N₂ or Ar).
3. S_N2 alkylation: Add 9-Bromo-1-nonanol (1.0 equiv) to the nucleophile solution (1.0–1.2 equiv nucleophile). Add base as required (e.g., K₂CO₃, Cs₂CO₃, or NaH, 1.2–2.0 equiv). Stir at room temperature to 60 °C (depending on nucleophile reactivity) for 2–16 h under inert atmosphere. Monitor by TLC or HPLC.
4. Workup: Cool the reaction to room temperature. Add water and extract with ethyl acetate (3×). Wash the combined organic layers with brine, dry over anhydrous Na₂SO₄, filter, and concentrate under reduced pressure.
5. Purification: Purify the crude product by flash column chromatography (silica gel, appropriate eluent) or by recrystallization as suitable.
6. Deprotection (if applicable): Remove any hydroxyl protecting group using standard conditions (e.g., TBAF in THF for TBS; p-TsOH in MeOH for THP).
7. Characterization: Confirm product identity and purity by ¹H NMR, ¹³C NMR, and MS. Key ¹H NMR indicators include: triplet near δ 3.4 ppm (–CH₂Br) and triplet near δ 3.6 ppm (–CH₂OH), with overlapping methylene signals at δ 1.3–1.9 ppm.

Application: Self-Assembled Monolayer (SAM) Formation on Gold Surfaces

ω-Bromoalkanols such as 9-Bromo-1-nonanol are useful precursors for preparing mixed or functionalized SAMs on gold substrates. The thiol-terminated analogue can be generated in situ or the bromo terminus can be converted to a thiol (–SH) via a Mitsunobu reaction or Gabriel synthesis sequence before SAM deposition.

General SAM deposition protocol:

1. Clean gold substrates (evaporated gold on silicon or mica) by UV-ozone treatment (15 min) or piranha solution (3:1 H₂SO₄:H₂O₂, 10 min; handle with extreme caution). Rinse with ultrapure water and dry under N₂.
2. Prepare a 1–5 mM solution of the thiol-terminated derivative (prepared from 9-Bromo-1-nonanol) in anhydrous ethanol.
3. Immerse clean gold substrates in the solution for 12–24 h at room temperature under N₂ or in a sealed vessel to prevent oxidation.
4. Remove substrates, rinse thoroughly with anhydrous ethanol, and dry gently under a stream of N₂.
5. Characterize the resulting SAM by contact angle goniometry, ellipsometry, XPS, or IRRAS as appropriate.

The terminal –OH group of the intact 9-Bromo-1-nonanol framework, when incorporated into a SAM, provides a hydrophilic surface for subsequent coupling chemistry or bio-functionalization.

Troubleshooting and Tips

Low S_N2 yield: Ensure anhydrous conditions; trace water can hydrolyze reactive intermediates. Consider switching to a more polar aprotic solvent (DMF or DMSO) and increasing the base equivalents. If elimination (E2) is a competing pathway, lower the reaction temperature and use a weaker base.

Premature lactonization: In the presence of strong base or Lewis acid, the hydroxyl group can cyclize onto an ester or activated intermediate. Protect the –OH as a silyl ether (TBSCl/imidazole) before reactions that risk intramolecular cyclization.

Discoloration of reagent: Yellowing over time indicates partial decomposition, possibly via HBr elimination. Use fresh material or re-purify by distillation under reduced pressure before critical experiments.

SAM quality issues: Incomplete monolayer coverage often results from insufficient substrate cleaning or solution age. Always use freshly prepared thiol solutions and thoroughly cleaned substrates. Overnight (18–24 h) incubation generally gives better-ordered SAMs than shorter times.

NMR interpretation: The –CH₂Br signal at ~3.4 ppm and the –CH₂OH signal at ~3.6 ppm can overlap with residual solvent signals in some deuterated solvents; CDCl₃ is recommended for clean interpretation.

Frequently asked questions

What is 9-Bromo-1-nonanol used for in organic synthesis?

9-Bromo-1-nonanol serves as a bifunctional C9 building block. The terminal alkyl bromide undergoes efficient Sₙ2 reactions with thiols, amines, malonates, and organometallic nucleophiles for chain elongation, while the hydroxyl group can be independently functionalized or protected. It is widely used in the synthesis of macrocycles, long-chain ethers, and surface-active molecules.

How should 9-Bromo-1-nonanol be stored to maintain stability?

Store 9-Bromo-1-nonanol in a tightly sealed container at 2–8 °C, away from light, moisture, and heat sources. Long-term exposure to light or elevated temperatures may promote HBr elimination and discoloration. If yellowing is observed, redistillation under reduced pressure is recommended before use in sensitive reactions.

Can 9-Bromo-1-nonanol be used directly for SAM formation on gold?

9-Bromo-1-nonanol cannot form SAMs directly on gold because SAM formation requires a thiol (–SH) head group that has strong affinity for gold surfaces. However, the bromo terminus can be converted to a thiol via nucleophilic substitution (e.g., using thiourea followed by hydrolysis, or via sodium hydrosulfide) to yield the corresponding 9-mercapto-1-nonanol, which then forms well-ordered hydroxyl-terminated SAMs on gold.

What solvents are compatible with 9-Bromo-1-nonanol reactions?

9-Bromo-1-nonanol is soluble in common polar aprotic solvents (DMF, DMSO, acetonitrile, THF) and chlorinated solvents (DCM, chloroform), all of which are suitable for Sₙ2 reactions. Protic solvents such as water or alcohols can compete with the nucleophile or promote solvolysis and should generally be avoided unless the reaction design specifically calls for them.

How can I confirm the purity of 9-Bromo-1-nonanol (B124493) upon receipt?

Upon receipt, check the Certificate of Analysis (CoA) provided with the product for purity data (typically assessed by GC or NMR). You can confirm identity by ¹H NMR in CDCl₃: look for a triplet at ~3.4 ppm (–CH₂Br), a triplet at ~3.6 ppm (–CH₂OH), and methylene multiplets at ~1.3–1.9 ppm. The absence of alkene signals (~5.0–6.0 ppm) confirms that HBr elimination has not occurred.

References

1. Ulman, A. Formation and Structure of Self-Assembled Monolayers. Chemical Reviews, 1996, 96(4), 1533–1554. doi:10.1021/cr9502357
2. Love, J. C.; Estroff, L. A.; Kriebel, J. K.; Nuzzo, R. G.; Whitesides, G. M. Self-Assembled Monolayers of Thiolates on Metals as a Form of Nanotechnology. Chemical Reviews, 2005, 105(4), 1103–1169. doi:10.1021/cr0300789
3. March, J. Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, 4th ed.; Wiley: New York, 1992.

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