CHAPTER 3
EXPERIMENTS
3 . 1 Reaction - media
The re a c tiv ity of sodium ions in e th e rific a tio n reaction of cellulose was studied by using various common organic solvents as reaction media. The solvents were chosen according to th e ir charac
te r is tic natures as follow s ะ
3.1.1 polar and non-polar properties
3.1 . 2 b o ilin g point and rate of evaporation
3.1 . 3 extent of harmfulnass on contact
They were also chosen w ith respect to a v a ila b ility in lo ca l market, economics and re u s a b ility .
In e th e rific a tio n , alcohols are frequently used as reaction media fo r most chemical transform ation both in la b o ra tirie s and in in d u s tria l processes. To search fo r more s c ie n tific inform ation, th is work was th is perfprmed by using alcohols and other organic solvents includ in g both polar and non-polar. Some ty p ic a l reaction media used in th is experiment were as follow s ;
polar methyl ethyl ketone acetone
iso-propyl alcohol n-propyl alcohol e th yl alcohol
1 0
non-polar benzene toluene cyclohexane n-hexane 3.2 Experimental Procedure
Throughout th is work, the experiments were carried out in the same manner but w ith various reaction media, d iffe re n t reaction times and at d iffe re n t temperatures. Treated cotton fuzz was used a3 source of c e llu lo se . Juice mixer (blender) was used fo r p u lve rize r as recom
mended by K. v/atanabe and M. Nakamura
(22).
Two sets of samples were prepared in th is experiment. One set was allowed the e th e rific a tio n to proceed a t26 + 2°c
fo r 1, 3» 5 and 7 days. The other was conducted at higher temperature (44 +2°c)
in an automatic incubator when temperature fluctua te d w ith in a narrow range.
In p ra ctice , a mole of ce llu lo se was w ell mixed w ith each in d i
vidual reaction medium as lis te d in 3*1* With continuous s tir rin g , 2 moles o f sodium hydroxide were added. The m ixture was cooled by using ice-w ater i f heat evolved during m ixing. Then one mole of monochloro- acetic acid was added and w ell mixed fo r about 15 minutes. The m ixture was transferred to a beaker which was covered by th in p la s tic sheet and kept a t
26
+2°c
fo r 1, 3, 5 and 7 days. A fte r each period, the product was sampled and filte re d through the Buchner funnel and, then, soakedin methyl alcohol. At th is p o in t, the a c id ity or a lk a lin ity of soaked s o lu t
ion (methyl alcohol) was inspected by using Bromothymol blue in d ic a to r.
1 1
I f the solu tion was acid (yellow c o lo r), i t was neutralized by sodium hydroxide so lu tio n . I f the so lu tio n was basic (blue c o lo r), i t was thus neutralized by hydrochloric acid. A fte r obtaining n eutral so lu tio n (green c o lo r), the m ixture was filte r e d and washed fo r several times w ith methyl alcohol to remove sodium chloride obtained as reaction by
product. The product was, then, a ir dried and kept in desiccator.
Another set of samples was prepared in the same manner as men
tioned above but the e th e rific a tio n was allowed to proceed at 44 + 2°c in automatic con tro lle d incubator (Baird & Tadlock L td ).
3.3 R e a ctivity of Sodium Ions in the System
At present, d ire c t- and indirect-m ethods are two available methods fo r determ ination of bound a lk a li involved in a lk a li treatment of cellulose and fo r determ ination the composition of a lk a li cellulose
(6 ). The disadvantage o f the tv/o methods is the d iffic u lty in perform
ing the experiment and an understanding of the chemical im p licatio n s of the structure of a lk a li ce llu lo se .
Since our main purpose of th is study is one concentrated to the e th e rific a tio n reaction of ce llu lo s e . Therefore, fu rth e r e th e rific a tio n a fte r a lk a li treatment o f ce llu lo se was carried out by using monochloro- acetic acid. Neglect the mechanism from which a lk a li ce llu lo se formed
(e ith e r CgH^02(0K)p.0Na or CgHy0o(0H)2.0H.Na0H), and of the errors due to experimental com plication as previously mentioned, the degree of su b s titu tio n (D .s .) o f sodium carboxymethyl group (-CHpCOONa) in a lk a li cellulose at the end of the f i r s t day of each sampl8 is used to pre d ict
1 2
the extent of the re a c tiv ity of sodium ions or a lk a li in forming
a lk a li ce llu lo se . The D .S .'s o f samples w ith the long’er reaction times are also used to p re d ict the inducing tendency or promotion fo r fu rth e r e th e rific a tio n of cellulose in the system. In other words, D.3. is assumed to be a scale fo r ju s tify in g the re a c tiv ity of sodium ions in e th e rific a tio n reaction of ce llu lo se .
In p ra ctice, about 0.5 E of product in n icke l cru cib le of known weight was dried at 110°c by using vacuum dryer (K arl Kolb- S c ie n tific Technical S upplies). A fte r 5 hours, the n icke l crucible and its cover were removed from dryer and kept in desiccator u n til they became cool. The crucible containing sample and cover were then weighed. The moisture content of the sample can be calculated by using equation (4).
The vacuum dried sample in n icke l crucible was ig n ite d w ith Bunsen burner u n til white s o lid appeared. The crucible and cover were c a re fu lly placed in to a beaker containing hot water and were then boiled. A fte r white s o lid was completely dissolved the crucible and it s cover were removed from so lu tio n and w e ll washed w ith
d is tille d water. Add 10 cm^ of ช.2 IT 1^2ร0^ in the so lu tio n then i t was evaporated to about 100 enr . A fte r cooling, the so lu tio n was titra te d w ith standard NaOH (about 0.2H) and w ith phenolphtha- le in as in d ic a to r. The D .s . of the product can thus be calculated by using equation (6).
