Detailed Methods for Drying and Purifying Common Organic Solvents in the Laboratory

Introduction

In organic chemistry experiments and industrial production, the quality of solvents often directly affects the success of reactions and the purity of products. High-purity organic solvents not only improve reaction efficiency but also avoid side reactions, ensuring accuracy and reproducibility of experimental results. This article systematically introduces the physical properties, common impurities, removal methods, and specific drying and purification procedures for commonly used organic solvents in laboratories. Through detailed process descriptions and analysis of precautions, it provides a comprehensive guide to handling organic solvents for laboratory personnel.

Purification and Drying of Acetone

Acetone (C3H6O) is an important polar aprotic solvent widely used in organic synthesis and extraction processes. Its boiling point is 56.2°C with a refractive index of 1.3588 and a relative density of 0.7899. Commercial acetone typically contains about 1% water along with trace amounts of methanol, acetaldehyde, etc., which can interfere with water-sensitive chemical reactions such as those involving Grignard reagents.

Potassium Permanganate Oxidation Method

Take 250ml industrial-grade acetone into a 500ml round-bottom flask; add 2.5g potassium permanganate powder. Install a reflux condenser and heat to gentle boiling state. Observe color changes: if potassium permanganate's purple color fades quickly, it indicates high levels of reducing impurities in acetone; additional potassium permanganate should be added until after refluxing for 30 minutes when purple does not fade anymore. After completion, switch to distillation apparatus to collect fractions at 55-56.5°C . The distillate must be dried over anhydrous potassium carbonate or anhydrous calcium sulfate for more than 12 hours before filtering again followed by distillation to obtain high-purity acetone. The key here is controlling the amount added; excessive reducing impurities will consume large quantities oxidizer prolonging treatment time while potentially leading to overoxidation of acetone itself—hence preliminary small-scale tests are recommended.

Silver Nitrate-Sodium Hydroxide Purification Method Transfer100mlacetontoa250mLseparatoryfunnelandadd4mLof10%silver nitrate solution followed by3..6 mLof1mol/L sodium hydroxide solution.Shake vigorouslyfor10minutes then let sit until layers separate.Discardthelower aqueous phase.Repeat washing operationsuntil there’s no obvious precipitate generated fromtheaqueous phase.The collectedacetoneshouldbedriedoveranhydrouscalcium sulfatefor24hoursbeforefinallydistillingto collectfractionsat55-56..5 °C. This method effectively removes aldehyde impurities through silver mirror reaction principles while shortening processing time comparedto oxidation methodbyabout50%.However,silver nitrateisexpensiveandproduceswastecontaining silversoitisrecommendedonlyforsmall-scalepurifications.Duringprocessing,itshouldbeconductedunderlight protectiontopreventdecompositionofsilver salts..

Deep Purification Process for Benzene

bBenzene (C6H6), as a basic aromatic hydrocarbon solvent has aboilngpointof80..1 °C,refractiveindexof1...5011,andrelativedensity0...87865.Commercially available benzene primarily contains thiophene(boiling point84°C)andtraceamountsofwater.Since thiophene’sboilingpointiscloseto thatofbenzene conventionaldistillationcannoteffectivelyseparateit,makingchemicalmethodsnecessary... n DetectionandRemovalOfThiophene n Take1 ml sampleofthebenzensubjecttomeasurementmixwith2 ml concentratedsulfuric acid containing2 mgindolequinonethen shake observeafterstanding.Ifthesulfuricacidlayerturnsbluegreenthisindicatespresenceofthethiophenimpurities.Removalmethodasfollows:Mixbenzenewithconcentrated sulfuric acidin7/ body volume thoroughlyshakeinaseparatory funnel where thiophenes undergo sulfonationreactionintoacidlayers.Repeattheoperation3-5timesuntilacid layer appearscolorlessandinodetectionusing indolequinonedetectio....Aftertreatment,thebenzeneremainswashedwith10% sodium carbonate solutionfollowedbywaterwashingtomaintainneutralitythen driedoveranhydrouschloridecalciumfor24hoursbeforecollectingfractionsat80 ° C... n ### In-depth Dehydration Treatment ...