## 2 Results and Discussion
Additionally, complete conversion of **1** into **3** was achieved under the same optimal conditions after 36 h. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Entry** & **Catalyst (mol \%) 1** & **LA/1-Pentanol** & **T (\({}^{\circ}\)C)** & **t (h)** & **C (\%) 2** \\ \hline
1 & 4.3 & & & & 5 & 29 \\
2 & 8 & & & & 43 \\
3 & 10 & & & & 50 \\ \hline
4 & 4.3 & & & & 12 & 32 \\
5 & 8 & & & & 51 \\
6 & 10 & & & & 57 \\ \hline
7 & 4.3 & & & & 24 & 53 \\
8 & 8 & & & & 64 \\
9 & 10 & & & & 65 (62) 3  \\ \hline
10 & 4.3 & & & & 5 & 22 \\
11 & 8 & & & & 38 \\
12 & 10 & & & & 46 \\ \hline
13 & 4.3 & & & & 12 & 33 \\
14 & 8 & & & & 39 \\
15 & 10 & & & & 52 \\ \hline
16 & 4.3 & & & & 24 & 43 \\
17 & 8 & & & & 46 \\
18 & 10 & & & & 58 \\ \hline
19 & 4.3 & & & & 5 & 50 \\
20 & 8 & & & & 51 \\
21 & 10 & & & & 56 \\ \hline
22 & 4.3 & & & & 12 & 55 \\
23 & 8 & & & & 60 \\
24 & 10 & & & & 64 \\ \hline
25 & 4.3 & & & & 24 & 66 \\
26 & 8 & & & & 70 \\
27 & 10 & & & & 76 (73)  \\ \hline
28 & 4.3 & & & & 5 & 38 \\
29 & 8 & & & & 41 \\
30 & 10 & & & & 44 \\ \hline
31 & 4.3 & & & & 12 & 50 \\
32 & 8 & & & & 52 \\
33 & 10 & & & & 54 \\ \hline
34 & 4.3 & & & & 24 & 58 \\
35 & 8 & & & & 60 \\
36 & 10 & & & & 67 \\ \hline \hline \end{tabular} 1: Referred to the amount of immobilized -SO\({}_{3}\)H moieties. 2: LA conversion to pentyl levulinate **3**, determined by  
\({}^{1}\)H-NMR analysis, using 4-bromoisable as internal standard; the remaining material was the unreacted mixture of **1** and **2**. 3: Isolated yield in parenthesis.  
\end{table} 
Table 3: Esterification reaction of LA **1** with 1-pentanol (**2**), catalyzed by A-15. Amberlyst-15 (10 mol %) allowed the lowest conversion at 90 \({}^{\circ}\)C when employing a 1:10 LA/alcohol molar ratio (Table 3, entry 36). Notably, the temperature increase led to a -10% decrease in Amberlyst-15 activity [54] (Table 3, entry 27 vs. entry 36). The effect of temperature increase on catalytic efficiency was greater for Aquivion mP98 than for PS-pTSOH (Table 2, entries 27 and 36 vs. Table 4, entries 27 and 36). Finally, Aquivion mP98 and PS-pTSOH (10 mol %, 1:10 LA/alcohol molar ratio) allowed a higher conversion increase in the range 5-12 h with respect to Amberlyst-15, at 70 \({}^{\circ}\)C as well as at 90 \({}^{\circ}\)C. This is exemplified by Table 4, entries 30 and 33 vs. Table 2, entries 30 and 33 vs. Table 3, entries 30 and 33. The influence of the reaction temperature on the efficiency of the catalysts is also represented in Figures 1 and 2. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Entry** & **Catalyst (mol \%) 1** & **LA/1-Pentanol** & **T \({}^{\circ}\)C** & **t (h)** & **C (\%) 2** \\ \hline
1 & 4.3 & & & 5 & 32 \\
2 & 8 & & & & 44 \\
3 & 10 & & & & 58 \\ \hline
4 & 4.3 & & & 12 & 54 \\
5 & 8 & & & & 60 \\
6 & 10 & & & & 62 \\ \hline
7 & 4.3 & & & 24 & 55 \\
8 & 8 & & & & 65 \\
9 & 10 & & & & 68 (64) 3 \\ \hline
10 & 4.3 & & & & 5 & 25 \\
11 & 8 & & & & 50 \\
12 & 10 & & & & 56 \\ \hline
13 & 4.3 & & & 12 & 50 \\
14 & 8 & & & & 65 \\
15 & 10 & & & & 67 \\ \hline
16 & 4.3 & & & 24 & 50 \\
17 & 8 & & & & 69 \\
18 & 10 & & & & 68 \\ \hline
19 & 4.3 & & & & 5 & 43 \\
20 & 8 & & & & 50 \\
21 & 10 & & & & 56 \\ \hline
22 & 4.3 & & & 12 & 50 \\
23 & 8 & 1:10 & 70 & & 12 & 50 \\
24 & 10 & & & & 70 \\ \hline
25 & 4.3 & & & & 24 & 55 \\
26 & 8 & & & & 73 \\
27 & 10 & & & & 80 \\ \hline
28 & 4.3 & & & & 5 & 50 \\
29 & 8 & & & & 50 \\
30 & 10 & & & & 51 \\ \hline
31 & 4.3 & & & & 12 & 55 \\
32 & 8 & & & & 58 \\
33 & 10 & & & & 72 \\ \hline
34 & 4.3 & & & & 24 & 60 \\
35 & 8 & & & & 65 \\
36 & 10 & & & & 83 (78) 3 \\ \hline \hline \end{tabular}  
* Referred to the amount of immobilized -SO\({}_{3}\)H moieties. 2 LA conversion to pentyl levilinate **3**, determined by 1H-NMR analysis, using 4-bromoanisole as internal standard; the remaining material was the unreacted mixture of **1** and **2**. 3 Isolated yield in parenthesis.  
\end{table} 
Table 4: Esterification reaction of LA **1** with 1-pentanol (**2**) catalyzed by PS-pTSOH.