Reaction #452421

Reaction equation

L-lactic acid

Acetic anhydride

DL-2-Hydroxycaproic acid

→

lactic acid

hydroxycaproic acid

Solvents

water

water

Conditions

Workup

1. 1
   Other0.043 mole) were placed in a reaction flask
2. 2
   Otherequipped with a distillation head and mechanical stirrer
3. 3
   Otherwas removed
4. 4
   Temperatureby heating at 80° C. for 14 hours
5. 5
   workup.DISTILLATIONExcess acetic anhydride and acetic acid were distilled off under low vacuum
6. 6
   workup.ADDITIONTetrahydrofuran/water (15 mL of 85/15; volume/volume) was added
7. 7
   Temperatureheating at 60° C. for 0.5 hour
8. 8
   OtherThe bulk of the solvent was removed by vacuum distillation on a rotary evaporator
9. 9
   workup.DISSOLUTIONThe resulting crude product was dissolved in chloroform (20 mL)
10. 10
    WashThe chloroform solution was washed twice with millipore water (5 mL)
11. 11
    Dryingdried with MgSO4
12. 12
    FiltrationThe mixture was filtered through a "d" fritted glass funnel
13. 13
    workup.DISTILLATIONthe solvent distilled from the polymer by rotary evaporation
14. 14
    OtherFinal traces of solvents were removed under high vacuum (0.4 mm Hg) on a Kugelrohr apparatus at 120° C.

Procedure

DL-2-Hydroxycaproic acid (1.00 gram, 0.0076 mole), and L-lactic acid (4.5 grams of a nominally 85% solution in water; 0.043 mole) were placed in a reaction flask equipped with a distillation head and mechanical stirrer. The flask was heated at 110° C. for 6 hours under low vacuum (aspirator) while water was removed. The temperature was then raised to 140° C. for 6 hours. Acetic anhydride (5.16 grams; 0.0506 moles) was added to the polymer, followed by heating at 80° C. for 14 hours. Excess acetic anhydride and acetic acid were distilled off under low vacuum. Tetrahydrofuran/water (15 mL of 85/15; volume/volume) was added with stirring and heating at 60° C. for 0.5 hour. The bulk of the solvent was removed by vacuum distillation on a rotary evaporator. The resulting crude product was dissolved in chloroform (20 mL). The chloroform solution was washed twice with millipore water (5 mL) and then dried with MgSO4. The mixture was filtered through a "d" fritted glass funnel and the solvent distilled from the polymer by rotary evaporation. Final traces of solvents were removed under high vacuum (0.4 mm Hg) on a Kugelrohr apparatus at 120° C. to provide acetyl-poly(DL-2-hydroxycaproic-co-L-lactic acid) with n=7.5 for lactic acid and 1.4 for hydroxycaproic acid, Mn=763, and Mw=1044 (by GPC).

Source