Тетраизобутоксисилан

Description

Tetraisobutoxysilane, Si(OCH₂CH(CH₃)₂)₄, is an isobutyl orthoester of silicic acid, a representative of a series of tetraalkoxysilanes. The substance reacts with water: alkoxy groups are hydrolyzed to release isobutanol, the resulting silanols condense into a three-dimensional polysiloxane network. The application of the entire class is based on this property - the production of coatings and materials based on silicon dioxide.

Basic Attributes

• CAS No.: 681-98-1
• Chemical formula: C16H36O4Si
• Molecular weight: 320.54014
• Exact weight: 320.54
• EU number: 211-658-5
• DSSTox ID: DTXSID30218297
• HS code: 2920909090
• PSA: 36.92000
• XLogP3: 4.11240
• Appearance according to the supplier’s card: “yellow melt”
• Density: 0.8855 g/cm³ at 20 °C
• Melting point: 214 °C (with decomposition) - supplier card value
• Boiling point: 255–258 °C at 760 Torr pressure
• Flash point: 77 °C (171 °F)
• Refractive index: 1.495
• Water solubility: Reacts with water

Chemical nature

The silicon atom is bonded to four isobutoxy groups. Hydrolysis proceeds stepwise: each group is replaced by a hydroxyl group with the elimination of isobutanol, after which the silanol fragments condense to form Si–O–Si bonds. The branched isobutyl radical shields silicon more strongly than linear alkyls, so hydrolysis proceeds more slowly than with methoxy and ethoxy analogues, and the process is easier to control over time.

Scope of application

• Tetraalkoxysilanes are used for the synthesis of coatings based on pure silicon dioxide with high hardness, chemical resistance and barrier properties
• Molecules with hydrolyzable –OR groups condense into a three-dimensional polysiloxane network - basic chemistry of sol-gel materials
• Source of silicon in the production of silica materials

Safety Information

• Hazard Statements: H315 - Causes skin irritation
• GHS classification, signal word on Hazard card: H315 (100%) - skin irritation (class "corrosion/skin irritation")
• Precautions: P261, P264, P271, P280, P302 + P352, P304 + P340, P305 + P351 + P338, P310, P312, P321, P332 + P313, P362, P403 + P233, P405, P501
• Basis of classification: aggregated GHS data from 4 companies for 1 notification to the ECHA C and L register; one notification may apply to several companies
• Hazard class code: R41; R37/38
• Safety instructions: S26; S37/S39
• Tags: Xi
• Stability: stable

Storage and handling

Direct indication of the card - the substance reacts with water, so the container is kept tightly closed, the opened package is purged with dry inert gas. Moisture in the air triggers hydrolysis, the product becomes cloudy and thickens until a gel is formed. A flash point of 77 °C classifies it as a flammable liquid: the warehouse is cool, ventilated, without ignition sources. Codes R41 and R37/38 indicate a risk of serious eye damage and irritation to the respiratory tract and skin, instructions S26, S37/S39 indicate the need to immediately rinse eyes with water in case of contact and wear gloves and eye and face protection when working.

Notes on the card data. First: the melting point of 214 °C with decomposition and the boiling point of 255–258 °C at atmospheric pressure are given - the values ​​​​are mutually contradictory. Second: the appearance is recorded as "yellow melt". Third: in some catalogs, the same CAS number is assigned to titanium isobutoxide; the gross formula C16H36O4Si, EC number 211-658-5 and the entire series of card synonyms (isobutyl silicate, tetraisobutyl orthosilicate, silicon tetraisobutoxide) clearly indicate a silicon compound. All values ​​are transferred from the original card without changes.