阅读说明：本技术 一种快速合成正溴丁烷的制备方法 (Preparation method for rapidly synthesizing n-bromobutane ) 是由 蒋历辉 邹应萍 于 2021-09-09 设计创作，主要内容包括：正溴丁烷的合成常以正丁醇、溴化盐和无机酸为原料,一般需要回流反应60.0min再将粗产物蒸出,再用水洗除盐、酸洗除原料醇和副产物丁烯等、水洗除酸、无水氯化钙干燥、蒸馏等步骤得到纯正溴丁烷。本发明公开了一种快速合成正溴丁烷的制备方法,以正丁醇、溴化盐和无机酸为原料,通过调整原料加料顺序,先让其中某两个原料加热至刚好回流,再迅速加入第三个原料,回流反应时间从60.0min缩短至5.0min,即可高产率、简便、绿色环保合成粗正溴丁烷,其核心在于先加正丁醇和无机酸至刚好回流,正丁醇在酸性高温条件下生成盐,此时再迅速加入溴化盐或氢溴酸,体系中立即产生Br～(-)进攻正丁醇盐得到粗产物正溴丁烷,将粗产物蒸出再进行后处理纯化步骤可得纯正溴丁烷。该方法操作简单,所用原料简单易得,合成工艺简便,节省时间和能源,绿色环保,降低了生产成本。(The synthesis of the n-bromobutane usually takes n-butanol, bromide salt and inorganic acid as raw materials, generally requires reflux reaction for 60.0min, then the crude product is evaporated, and the pure n-bromobutane is obtained by the steps of washing for removing salt, washing for removing raw material alcohol and by-product butene, washing for removing acid, drying anhydrous calcium chloride, distilling and the like. The invention discloses a preparation method for rapidly synthesizing n-bromobutane, which takes n-butanol, bromide salt and inorganic acid as raw materials, and by adjusting the charging sequence of the raw materials, firstly heating certain two raw materials to be just refluxed, then rapidly adding the third raw material, and shortening the reflux reaction time from 60.0min to 5.0min, namely the product with high purityThe method for synthesizing the crude n-bromobutane with high yield, simplicity, convenience, environmental protection and the key point is that n-butanol and inorganic acid are added to be just refluxed firstly, and the n-butanol is generated under the acidic high-temperature condition Salt, in which case a bromide or hydrobromic acid is added rapidly and Br is generated immediately in the system ‑ Attacking n-butanol)

1. A method for rapidly preparing n-bromobutane is characterized in that through adjusting the sequence of raw material feeding, one of two raw materials is heated to be just refluxed, then the third raw material is rapidly added, and the reflux reaction time can be shortened from 60.0min to 5.0 min.

2. The method for rapidly preparing n-bromobutane as claimed in claim 1, which is characterized in that n-butanol and inorganic acid solution are added to the reaction mixture just under reflux, and the n-butanol is generated under acidic proton high temperature conditionSalt, bromide salt, Br in the system^-Attacking n-butanolSalt is obtained to obtain n-bromobutane, reflux reaction is carried outThe reaction is completed in 5.0min, and the reflux device is changed into a distillation device to begin to distill the crude product.

3. The method for preparing n-bromobutane according to claim 1, characterized in that inorganic acid solution with mass fraction of 20% -80% is prepared first.

4. The method according to claim 3, wherein the inorganic acid is concentrated sulfuric acid, concentrated phosphoric acid, concentrated nitric acid, hydrobromic acid, or the like.

5. The method of claim 1, wherein n-butanol and the mineral acid are refluxed to a temperature at which n-butanol is formed under acidic high temperature conditionsThe ratio of salt, n-butanol and mineral acid is n-butanol: n inorganic acid ═ 1.0: 2.0-1.0: 3.5.

6. the process for producing n-bromobutane according to claim 1, characterized in that when the reaction system just flows back, bromide salt or hydrobromic acid, Br, is added immediately^-Attacking n-butanolObtaining n-bromobutane by salting, wherein the proportion of n-butyl alcohol to bromide salt is n-butyl alcohol: n-bromide salt ═ 1.0: 1.0-1.0: 1.5 or n-butanol: n-hydrobromic acid ═ 1.0: 1.0-1.0: 1.5.

7. the method for preparing n-bromobutane according to claim 6, wherein the bromide salt is lithium bromide, sodium bromide, potassium bromide, etc., and the concentration of hydrobromic acid is 5% -50%.

8. The method for preparing n-bromobutane according to claim 1, characterized in that the reflux reaction is stopped after 5.0min of adding bromide salt and the reflux device is changed to a distillation device to distill off the crude product.

9. The method for preparing n-bromobutane according to claim 8, characterized in that the purification step of the crude product obtained by distillation is to wash with water to remove inorganic salts and acids in the system, then wash with strong inorganic acid to remove the remaining raw materials of n-butanol, by-products of 1-butene, 2-butene, etc., then wash with water to remove the remaining strong inorganic acid, then further wash with saturated alkaline solution to remove the remaining acid, then wash with water to remove sodium bicarbonate in the system, and finally dry with drying agents such as anhydrous calcium chloride, anhydrous potassium carbonate, etc.

10. The method for preparing n-bromobutane as claimed in claim 9, wherein the alkaline solution used is sodium hydroxide, sodium carbonate, sodium bicarbonate or the like.

11. The method for preparing n-bromobutane according to claim 9 is characterized in that the crude product is further purified by a distillation apparatus to obtain a pure product after purification steps of water washing for desalting, acid washing for removing raw material alcohol and by-product butene, water washing for removing acid, alkali washing for further removing residual acid, water washing for removing alkali, drying and the like, and fractions with boiling points of 99-102 ℃ are collected.

Technical Field

The invention belongs to the technical field of chemical basic raw material synthesis, and particularly relates to a preparation method for rapidly synthesizing n-bromobutane.

Background

N-bromobutane, also known as n-butyl bromide, 1-n-butyl bromide or n-butyl bromide, is a colorless and transparent oily liquid which is easily soluble in alcohols and ethers. As an important chemical raw material, the catalyst has wide application in industrial synthesis. Can be used as solvent and alkylating agent and intermediate in organic synthesis; used for synthesizing organic phosphine compound tributyl phosphine, phase transfer catalyst and surfactant tetra-n-butyl ammonium bromide; is also a main raw material for synthesizing an important organic reaction intermediate o-dialkoxybenzene; can also be used as the raw material of plastic ultraviolet absorbent and plasticizer; used as a raw material for medicines; dye raw materials, raw materials for preparing functional pigments (such as pressure sensitive pigments, thermal sensitive pigments, dichromatic pigments for liquid crystal); semiconductor intermediate raw materials; organic synthesis raw materials. Because n-bromobutane has a plurality of purposes, the research on the synthesis principle of n-bromobutane and the improvement of the synthesis process of n-bromobutane have important practical significance.

The classical preparation method of n-bromobutane is to synthesize n-bromobutane by using sodium bromide, concentrated sulfuric acid and n-butanol as raw materials, and the main reaction chemical equation of the preparation process is as follows:

NaBr+H₂SO₄→HBr+NaHSO₄

formula 1. conventional reaction formula for synthesis of n-bromobutane

And the side reactions mainly comprise the following four reactions:

2HBr+H₂SO₄→Br₂+SO₂+2H₂O

formula 2 formation of bromine

Formation of n-butenes of formula 3

Formation of butyl Ether of formula 4

Formation of the bromobutanes of formula 5.2

From the above, the conventional synthesis of n-bromobutane is obtained by reacting n-butanol with hydrobromic acid, and the hydrobromic acid is an extremely volatile inorganic acid, so that the hydrobromic acid generated by the reaction of sodium bromide and sulfuric acid is directly involved in the reaction during the preparation. In the reaction, sulfuric acid is both a catalyst for the reaction and a reactant for producing hydrogen bromide. However, hydrogen bromide has a certain reducibility, and when the concentration of sulfuric acid is high, it can be oxidized (formula 2). In addition, sulfuric acid has strong dehydration property, and when the concentration is too high, n-butanol may be converted into alkene (formula 3) and ether (formula 4). As the 2-degree carbenium ion has more sigma-p hyperconjugation than the 1-degree carbenium ion and has better stability, the n-butyl carbenium ion is rearranged to generate the sec-butyl carbenium ion in the reaction process, and Br is generated at the moment^-And then reacted therewith to produce 2-bromobutane (formula 5).

As the preparation reaction has more side reactions and generates more byproducts, after the reaction is finished, the crude product is firstly distilled out, and then the byproducts are removed one by adopting a separating funnel to wash step by step, wherein the washing process is shown in figure 1. Washing with water of the same volume to remove most of bromine, hydrogen bromide and n-butanol, carefully layering, transferring the organic layer to another dry separating funnel, washing with concentrated sulfuric acid of the same volume to remove n-butyl ether and residual n-butanol (forming protonated ether and alcohol and dissolving in excess sulfuric acid), separating the sulfuric acid layer as much as possible, washing the organic layer with water of the same volume to remove residual sulfuric acid, washing with saturated sodium bicarbonate solution, and washing with water to remove NaHSO₄With excess NaHCO₃And (4) after the residues are completely layered, transferring the residues into a dry conical flask, and drying the residues by using anhydrous calcium chloride, wherein the whole process needs to pay attention to the position of an organic layer.

FIG. 1 shows a schematic view of a

In order to optimize the preparation reaction of n-bromobutane, the proportion of sodium bromide, concentrated sulfuric acid, n-butanol and water is researched by more subject groups. The reaction of Yuchumei and the like with addition of sulfuric acid can produce a high yield of n-bromobutane, but the addition of sulfuric acid in the reaction is easy to control under laboratory conditions, and local carbonization is easily caused when a large amount of sulfuric acid is added in industrial synthesis. Thus, the subject group tried to compensate for the reduction in sulfuric acid concentration due to the water produced by the reaction by adding an excess of sulfuric acid, but with an excess of H₂SO₄More sodium bromide is required and this reagent overdose scheme does not follow green chemistry principles. Wangchao and the like intend to use red phosphorus and liquid bromine to replace concentrated sulfuric acid to react with sodium bromide to generate hydrogen bromide, and investigate the preparation of n-bromobutane by using n-butyl alcohol, red phosphorus and liquid bromine as raw materials in the presence of catalytic amount of concentrated sulfuric acid, wherein the optimal feeding amount is as follows: 0.2 mol of n-butanol 1, 0.053mol of red phosphorus, 0.06mol of water, 0.08mol of liquid bromine and 0.046mol of concentrated sulfuric acid, and the reflux reaction is carried out for 2.0h, wherein the yield is 83 percent. However, liquid bromine has extremely high volatility, extremely high corrosivity, extremely high hazard to people and extremely dangerous operation.

At present, the synthesis optimization of the n-bromobutane is limited to increasing the dosage of concentrated sulfuric acid and sodium bromide, or investigating the influence of the addition mode of the concentrated sulfuric acid on the yield of the n-bromobutane, or considering that the concentrated sulfuric acid has stronger oxidability, the acidity can be maintained by supplementing concentrated phosphoric acid, and the oxidability of a system is not increased, but the research schemes are different greatly, and the preparation of the n-bromobutane is not essentially improved, so that the research on the synthesis scheme of the n-bromobutane, which has low cost, stable quality, simple and convenient process and environmental friendliness, has important research value.

Disclosure of Invention

The invention aims to provide a novel method for quickly synthesizing n-bromobutane by taking n-butanol, bromide salt and inorganic acid as raw materials, adjusting the feeding sequence of the raw materials, shortening the heating reflux reaction from 60.0min to 5.0min and saving the reaction time greatly, and the method is simple and easy to operate, has an environment-friendly process and can greatly save the reaction time.

The invention provides a method for quickly synthesizing n-bromobutane, which comprises the following steps:

(1) preparation of an acid solution: taking 100.0mL of purified water into a 500.0mL beaker, slowly pouring 100.0mL of high-concentration acid while stirring, fully cooling to room temperature after all the acid is added, and transferring the mixture into a clean glass bottle with a plug for later use.

(2) Preparation of n-bromobutane: 6.2mL (5.0g,0.068mol) of n-butanol as a reaction raw material and 20.0mL of the acid solution prepared above were added to a 100mL three-necked flask, a stirrer was placed, stirring was started, a reflux-aspiration reaction apparatus (FIG. 2) was rapidly assembled, and a 5% alkali solution was used as an absorbent. The reaction was heated until there was reflux of droplets in the flask, at which time the side-port stopper of the three-necked flask was pulled open and the weighed 0.08mol of finely ground bromide salt was added rapidly. The reaction was stopped at reflux reaction time of 5.0min, using a stopwatch.

(3) Distillation of the crude product: after the reaction system is cooled slightly, the reaction system is transferred into a single-neck flask from a three-neck flask, a distillation device (figure 3) is assembled, a crude product of n-bromobutane is distilled out, the timing is accurate, and the distillation is finished within 10.0 min.

FIG. 2

FIG. 3

(4) Washing a crude product: transferring the distillate into a separating funnel, washing with water of the same volume, separating, carefully transferring the organic layer into another dry separating funnel, washing with concentrated sulfuric acid of the same volume, removing the sulfuric acid layer as much as possible, washing the organic layer with water of the same volume, saturated sodium bicarbonate solution and water in sequence, and drying with anhydrous calcium chloride.

(5) Distilling to obtain pure n-bromobutane: transferring the dried liquid into a dry distillation flask, assembling a clean and dry distillation device, collecting the fraction at 99-102 ℃, and weighing.

In a preferred embodiment, the inorganic acid in step (1) is concentrated sulfuric acid, concentrated phosphoric acid, concentrated nitric acid, hydrobromic acid, or the like.

Preferably, the core operation of step (2) is that n-butanol and an acid solution are added into a three-neck flask, and are heated until the reflux just appears, and the n-butanol is generated under the acidic proton high-temperature conditionSalt, bromide salt and Br in the reaction system^-Attacking n-butanolThe salt gives n-bromobutane.

Preferably, in the step (2), the bromide salt is a bromide salt such as lithium bromide, sodium bromide, potassium bromide, or the like.

In a preferred embodiment, the core operation of step (2) is that n-butanol and acid solution are added into a three-neck flask, heated to just reflux, and then bromide salt is added from a side port immediately.

Preferably, the ratio of n-butanol to inorganic acid in the step (2) is n-butanol: n inorganic acid ═ 1.0: 2.0-1.0: 3.5, the ratio of n-butanol to bromide salt is n-butanol: n-bromide salt ═ 1.0: 1.0 to 1.0: 1.5.

in a preferable scheme, after the reflux reaction is carried out for 5.0min in the step (3), the system is slightly cold, the reaction system is transferred into a single-neck flask as soon as possible to prevent the system from being cooled, and NaHSO₄The cooling agglomerates hinder the liquid transfer. The crude product is distilled off using a distillation apparatus, without the use of a thermometer.

Preferably, in the step (4), the purification step of the crude product obtained by distillation includes water washing to remove inorganic salts and acids in the system, washing with inorganic strong acid to remove residual raw materials such as n-butanol, byproduct 1-butene, 2-butene and the like, water washing to remove residual inorganic strong acid, further washing with saturated alkaline solution to remove residual acid, washing with water to remove sodium bicarbonate in the system, and finally drying with anhydrous calcium chloride.

Compared with the prior art, the invention has the beneficial technical effects that:

the method has the advantages of convenient operation, low cost, high efficiency and easy realization of industrial production.

Drawings

FIG. 1 shows a scheme for separating n-bromobutane (the upper and lower layers of the organic layer in each washing are shown in the figure)

FIG. 2. three-necked flask is connected with a reflux heating device with gas absorption

FIG. 3. distillation apparatus

FIG. 4 reaction mechanism of post-addition of sodium bromide

FIG. 5 shows a reflux heater with gas absorption in a single-neck flask

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments.

The present invention will be described in more detail below.

The invention provides a preparation method of watermelon ketone, which comprises the following steps:

(1) preparing a sulfuric acid solution: taking 100.0mL of purified water into a 500.0mL beaker, slowly pouring 100.0mL of concentrated sulfuric acid while stirring under the cooling of an ice-water bath, safely operating to prevent sulfuric acid from splashing, completely cooling to room temperature, transferring into a clean glass bottle with a plug for standby, and finishing use within three days.

(2) Preparation of n-bromobutane: and (3) heating the oil bath kettle to 140 ℃, starting fast-heat mode rapid heating, and after the oil bath kettle is stable. 6.2mL (5.0g,0.068mol) of n-butanol as a reaction raw material and 20.0mL of the prepared sulfuric acid solution were added to a 100mL three-necked flask, a stirrer was placed, stirring was started, a reflux-suction reaction apparatus (FIG. 2) was rapidly assembled, and a 5% alkali solution was used as an absorbent. Heating the reaction system until liquid drops in the reaction bottle flow back, at the moment, pulling out a side-opening stopper of the three-neck flask, and quickly adding weighed 0.08mol of ground sodium bromide (8.3g), if sodium bromide remains on the bottle wall, quickly sucking the liquid in the reaction bottle and flushing the liquid into the reaction system. The reaction was stopped at reflux reaction time of 5.0min, using a stopwatch.

(3) Distillation of the crude product: after the reaction system had cooled slightly, the reaction system was transferred from the three-necked flask to a single-necked flask (which had to be hot otherwise NaHSO)₄Cooling lumps hamper liquid transfer). Assembling a distillation device (figure 3), distilling out the crude product of the n-bromobutane, and accurately meteringThen, distillation was completed in 10.0 min. The residual solution should be poured into acid liquor recovery bottle while it is hot to prevent NaHSO₄The cake was cooled in the flask.

(4) Washing a crude product: transferring the distillate into a separating funnel, washing with an equal volume of water, separating, carefully transferring the organic layer into another dry separating funnel, washing with an equal volume of concentrated sulfuric acid, removing the sulfuric acid layer as much as possible, washing the organic layer with equal volumes of water, saturated sodium bicarbonate solution and water in sequence, and drying with anhydrous calcium chloride (calcium chloride should be added in a proper amount and intermittently oscillated until the liquid is clear).

(5) Distilling to obtain pure n-bromobutane: transferring the dried liquid into a dry distillation flask, assembling a clean and dry distillation device, collecting the fraction at 99-102 ℃, and weighing.

The solvent used in the invention is one of concentrated sulfuric acid, concentrated nitric acid, concentrated hydrochloric acid and hydrobromic acid; preferably concentrated sulfuric acid.

The bromide salt added in the invention is one of sodium bromide, potassium bromide and lithium bromide, preferably sodium bromide.

The alkaline solution used for washing the crude product in the present invention is sodium hydroxide, potassium hydroxide, sodium bicarbonate, sodium carbonate, preferably sodium bicarbonate.

The drying agent used in the present invention is calcium chloride or magnesium sulfate, preferably calcium chloride.

In order to verify that the reaction can be finished by adding n-butanol and sulfuric acid and heating until reflux just occurs, then adding sodium bromide, and carrying out reflux reaction for 5.0min, the patent considers the influence of different reaction times on the reaction, experiments of 5.0min, 10.0min, 15.0min, 20.0min and 25.0min are carried out by adopting the same reaction conditions, and the yield of the n-bromobutane is listed in table 1.

TABLE 1 post addition of sodium bromide, yield as a function of reaction time

As can be seen from Table 1, the n-butanol and sulfuric acid solution were added and heated to reflux, then sodium bromide was added rapidly, and after 5.0min of reaction, the crude product was distilled off by using a distillation apparatus, and the yield of n-bromobutane was almost constant. Meanwhile, in order to ensure that the reaction time has influence on the yield, the n-butanol and sulfuric acid solution is added and heated for 5.0min until the solution just flows back, and then the time for distilling the crude product is strictly controlled to be 10.0 min. The experimental results in Table 1 prove that the reaction needs to be performed in 60.0min or more under reflux in the ordinary n-bromobutane preparation experiment, and can be completed smoothly in 5.0 min. The reaction mechanism is presumed to be as follows (fig. 4):

FIG. 4

The n-butyl alcohol and the sulfuric acid are added into a reaction system firstly, and at the moment, sodium bromide is not contained in the system, and hydrogen bromide cannot be generated, so that the reaction (shown as a formula 2) that the hydrogen bromide is oxidized by the sulfuric acid cannot occur. At the moment, the heating reflux of the system is favorable for the protonation of the n-butyl alcohol under the acidic condition to formSalt, OH group which is less readily removable^－Conversion to H which leaves more readily₂And O, the step is the speed-dependent step for preparing the n-bromobutane. On the other hand, the timing of the addition of sodium bromide is critical whenAfter salt formation, at which point sodium bromide is added to generate Br immediately^-And attack of positively charged carbon atoms to promote H₂The leaving of O produces n-bromobutane as in the darkened, bold reaction scheme (1) of FIG. 4. When n-butanol is presentAfter the salt formation, if sodium bromide is not added to the reaction system at all times, n-butanol may attack the positively charged carbon atom to form butyl ether, as shown in reaction scheme (2) of FIG. 4. Also a reaction scheme, H₂O is removed to form 1 n-butyl carbenium ion, which in turn removes beta-H to form 1-butene, as shown in FIG. 4 as the italic reaction scheme (3).

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available.

The invention is further illustrated, but not limited, by the following description and the accompanying drawings.

Comparative example 1(3 raw materials added simultaneously to the reaction System)

A50 mL round-bottomed flask was charged with 8.3g (0.08mol) of finely divided sodium bromide, 6.2mL (5.0g,0.068mol) of n-butanol and a stirrer, and a mixed solution of 10mL of cooled concentrated sulfuric acid and 10mL of water (concentrated sulfuric acid was slowly added to water with stirring and cooled in a cold water bath) which had been previously mixed was charged into the flask, and a reflux-suction apparatus (FIG. 5) was installed, using a 5% sodium hydroxide solution as an absorbent. Magnetic stirring, and refluxing in silicon oil bath for 35 min. After the reaction is finished, slightly cooling, changing into a distillation device, distilling to obtain a crude product of n-bromobutane (the residual liquid is poured into an acid liquor recovery bottle while the residual liquid is hot, otherwise a byproduct of NaHSO₄Cooling the cake).

FIG. 5

Transferring the distillate into a separating funnel, washing with an equal volume of water, separating, carefully transferring the organic layer into another dry separating funnel, washing with an equal volume of concentrated sulfuric acid, removing the sulfuric acid layer as much as possible, washing the organic layer with equal volumes of water, saturated sodium bicarbonate solution and water in sequence, and drying with anhydrous calcium chloride (intermittent oscillation until the liquid is clear). Transferring the dried liquid into a dry distillation flask, distilling with a clean and dry distillation device, and collecting the fraction at 99-102 ℃. The weight was 3.53 g.

Comparative example 2 (post-addition of n-butanol)

A100 mL three-necked flask was charged with 8.3g (0.08mol) of finely ground sodium bromide as a reaction material and 20.0mL of an acid solution prepared according to the experimental step (1) of the embodiment, and a stirrer was placed therein, and the reflux-aspiration reaction apparatus (FIG. 2) was rapidly assembled by starting stirring, using a 5% alkali solution as an absorbent. Heating the reaction system until liquid drops in the reaction bottle reflux, pulling out a side-port stopper of the three-neck flask, quickly pouring the weighed 6.2mL (5.0g,0.068mol) of n-butanol, timing by using a stopwatch, and stopping the reaction after the reflux reaction time is 5.0 min. After the reaction system is slightly cooled, the reaction system is transferred into a single-neck flask from a three-neck flask, a distillation device (figure 3) is assembled, a crude product of n-bromobutane is distilled out, the timing is accurate, and the distillation is finished within 10.0 min.

Transferring the distillate into a separating funnel, washing with an equal volume of water, separating, carefully transferring the organic layer into another dry separating funnel, washing with an equal volume of concentrated sulfuric acid, removing the sulfuric acid layer as much as possible, washing the organic layer with equal volumes of water, saturated sodium bicarbonate solution and water in sequence, and drying with anhydrous calcium chloride (intermittent oscillation until the liquid is clear). Transferring the dried liquid into a dry distillation flask, distilling with a clean and dry distillation device, and collecting the fraction at 99-102 ℃. The weight was 2.57 g.

Comparative example 3 (post-addition of sulfuric acid)

A100 mL three-necked flask was charged with 6.2mL (5.0g,0.068mol) of n-butanol and 8.3g (0.08mol) of finely divided sodium bromide, a stirrer was placed, the stirrer was turned on, and a reflux-aspiration reaction apparatus (FIG. 2) was rapidly assembled using a 5% alkali solution as an absorbent. Heating the reaction system until liquid drops in the reaction bottle flow back, pulling out a side-opening stopper of the three-neck flask, quickly pouring the weighed 20.0mL of acid solution, timing by adopting a stopwatch, and stopping the reaction when the reflux reaction time is 5.0 min. After the reaction system is slightly cooled, the reaction system is transferred into a single-neck flask from a three-neck flask, a distillation device (figure 3) is assembled, a crude product of n-bromobutane is distilled out, the timing is accurate, and the distillation is finished within 10.0 min.

Transferring the distillate into a separating funnel, washing with water with the same volume, transferring the organic layer into another dry separating funnel, washing with concentrated sulfuric acid with the same volume, washing the organic layer with water, saturated sodium bicarbonate solution and water with the same volume in sequence, and drying with anhydrous calcium chloride. Distilling with a clean and dry distillation device, and collecting the fraction at 99-102 ℃. Weigh 2.52 g.

Example 1 (post-addition of sodium bromide)

Taking 10.0mL of purified water into a 50.0mL beaker, slowly pouring 10.0mL of concentrated sulfuric acid while stirring under the cooling of ice-water bath, safely operating to prevent sulfuric acid from splashing, and completely cooling to room temperature for later use.

And (3) heating the oil bath kettle to 140 ℃, starting fast-heat mode rapid heating, and after the oil bath kettle is stable. A100 mL three-necked flask was charged with 6.2mL (5.0g,0.068mol) of n-butanol as a reaction raw material and 20.0mL of the sulfuric acid solution prepared above, and a stirrer was placed therein, and the reflux-aspiration reaction apparatus (FIG. 2) was rapidly assembled with 5% sodium hydroxide solution as an absorbent by turning on the stirrer. Heating the reaction system until liquid drops in the reaction bottle flow back, at the moment, pulling out a side-opening stopper of the three-neck flask, quickly adding weighed and ground sodium bromide (8.3g, 0.08mol), and if sodium bromide remains on the bottle wall, quickly sucking the liquid in the reaction bottle and flushing the liquid into the reaction system. The reaction was stopped at reflux reaction time of 5.0min, using a stopwatch.

After the reaction system had cooled slightly, the reaction system was transferred from the three-necked flask to a single-necked flask (which had to be hot otherwise NaHSO)₄Cooling lumps hamper liquid transfer). And (3) assembling a distillation device (figure 3), distilling out the crude product of the n-bromobutane, accurately timing, and finishing the distillation within 10.0 min. The residual solution should be poured into acid liquor recovery bottle while it is hot to prevent NaHSO₄The cake was cooled in the flask. Transferring the distillate into a separating funnel, washing with an equal volume of water, separating, carefully transferring the organic layer into another dry separating funnel, washing with an equal volume of concentrated sulfuric acid, removing the sulfuric acid layer as much as possible, washing the organic layer with equal volumes of water, saturated sodium bicarbonate solution and water in sequence, and drying with anhydrous calcium chloride (calcium chloride should be added in a proper amount and intermittently oscillated until the liquid is clear). And finally transferring the dried liquid into a dry distillation flask, assembling a clean and dry distillation device, collecting the fraction at 99-102 ℃, and weighing 4.26 g.

Example 2 (post-addition of sodium bromide)

Taking 100.0mL of purified water into a 500.0mL beaker, slowly pouring 100.0mL of concentrated sulfuric acid while stirring under the cooling of an ice-water bath, safely operating to prevent sulfuric acid from splashing, completely cooling to room temperature, transferring into a clean glass bottle with a plug for standby, and finishing use within three days.

And (3) heating the oil bath kettle to 140 ℃, starting fast-heat mode rapid heating, and after the oil bath kettle is stable. A100 mL two-necked flask was charged with 6.2mL (5.0g,0.068mol) of n-butanol as a reaction raw material and 20.0mL of the sulfuric acid solution prepared above, and a stirrer was placed therein, and the stirrer was turned on, and a reflux-suction reaction apparatus was rapidly assembled using a 5% sodium hydroxide solution as an absorbent. The reaction system is heated until the liquid drops in the reaction bottle reflux, at the moment, the side-mouth stopper of the two-neck flask is pulled out, and weighed and ground sodium bromide (8.3g, 0.08mol) is rapidly added, if the sodium bromide remains on the bottle wall, the liquid in the reaction bottle needs to be rapidly sucked and washed into the reaction system. The reaction was stopped at 10.0min of reflux reaction time, timed with a stopwatch.

After the reaction system had cooled slightly, the reaction system was transferred from the two-necked flask to a single-necked flask (which had to be hot otherwise NaHSO)₄Cooling lumps hamper liquid transfer). And assembling a distillation device, distilling out the crude product of the n-bromobutane, accurately timing, and finishing distillation within 10.0 min. The residual solution should be poured into acid liquor recovery bottle while it is hot to prevent NaHSO₄The cake was cooled in the flask. Washing the distillate with water, acid washing, water washing, drying, distilling and the like to obtain pure n-bromobutane, collecting the fraction at 99-102 ℃, and weighing 4.22 g.

Example 3 (post-addition of sodium bromide)

Taking 100.0mL of purified water into a 500.0mL beaker, slowly pouring 100.0mL of concentrated sulfuric acid while stirring under the cooling of an ice-water bath, safely operating to prevent sulfuric acid from splashing, completely cooling to room temperature, transferring into a clean glass bottle with a plug for standby, and finishing use within three days.

And (3) heating the oil bath kettle to 140 ℃, starting fast-heat mode rapid heating, and after the oil bath kettle is stable. A100 mL three-necked flask was charged with 6.2mL (5.0g,0.068mol) of n-butanol as a reaction raw material and 20.0mL of the sulfuric acid solution prepared above, and a stirrer was placed therein, and the stirrer was turned on, and a reflux-suction reaction apparatus was rapidly assembled using a 5% sodium hydroxide solution as an absorbent. Heating the reaction system until liquid drops in the reaction bottle flow back, at the moment, pulling out a side-opening stopper of the three-neck flask, quickly adding weighed and ground sodium bromide (8.3g, 0.08mol), and if sodium bromide remains on the bottle wall, quickly sucking the liquid in the reaction bottle and flushing the liquid into the reaction system. The reaction was stopped at 15.0min of reflux reaction time, timed with a stopwatch.

After the reaction system is cooled slightly, the reaction system is transferred from the three-neck flask to the single-neck flask (the reaction system must be transferred to the three-neck flask when the reaction system is stillThermal or else NaHSO₄Cooling lumps hamper liquid transfer). And assembling a distillation device, distilling out the crude product of the n-bromobutane, accurately timing, and finishing distillation within 10.0 min. The residual solution should be poured into acid liquor recovery bottle while it is hot to prevent NaHSO₄The cake was cooled in the flask. Washing the distillate with water, acid washing, water washing, drying, distilling and the like to obtain pure n-bromobutane, collecting the fraction at 99-102 ℃, and weighing 4.24 g.

Examples 4 to 5

Examples 4-5 the same preparation as in example 3 was used, with only the reaction times being different compared to example 3:

the above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-described embodiments. Modifications and variations that may occur to those skilled in the art without departing from the spirit and scope of the invention are to be considered as within the scope of the invention.