Class number, name and grade
Please draw a device for synthesizing 2- methyl -2- hexanol.
2. When preparing n-bromobutane, move the crude product into a separating funnel, and sequentially use (1) 10ml water (2)8ml concentrated sulfuric acid (3) 10ml water (4) 10ml saturated sodium bicarbonate solution (5)/kloc-0.
Answer: the first water washing: dilute the solute in the water layer (such as HBr, Br2, SO2, n-butanol, etc. ), and reduce the relative density of the water layer, which is beneficial to the precipitation of n-bromobutane to the lower layer. (N-bromobutane in the lower layer)
Washing with concentrated sulfuric acid: washing off unreacted n-butanol and n-butyl ether, a side reaction product. (n-bromobutane is in the upper layer)
Second water washing: water-soluble substances such as hydrobromic acid, sulfuric acid and residual n-butanol (solubility in water is about 8%) in the crude product are washed away. (N-bromobutane in the lower layer)
10%Na2CO3 solution washing: further wash off acidic substances, such as sulfuric acid and hydrobromic acid. (N-bromobutane in the lower layer)
The third water washing: wash away the residual water-soluble substances such as Na2CO3. (N-bromobutane in the lower layer)
What is the function of recrystallization? What is the principle? How to detect the purity of products after recrystallization?
A: (1) It can be further separated and purified.
(2) Its principle is to remove impurities by using the different solubility of each component in the same solvent.
3) Determine the melting range after recrystallization. Generally, the melting range of pure substances is 1-2℃
4. What is steam distillation? What is its purpose? What are the advantages compared with atmospheric distillation? What conditions must its raw materials meet? How to judge whether the substance to be steamed has been steamed?
Answer: (1) Steam distillation is a process in which water is used as the component of mixed liquid, and substances that are basically insoluble in water are distilled out when mixed with water at a temperature lower than 100℃. ..
(2) Its purpose is to separate and purify organic compounds.
⑶ Its advantage is that the required organic matter can be distilled from the mixture at a lower temperature, thus avoiding the loss caused by atmospheric distillation.
(4) Its raw materials must have: ① Insoluble or insoluble in water; (2) * * * does not react with water when boiling; (3) at 100℃, there must be a certain steam pressure (not less than10 mm Hg); (4) When the distillate has no obvious oil drops and is clear and transparent, it can be judged that the substance to be steamed is cooked.
20 10-20 1 1 organic chemistry examination for applied chemistry in the first semester of the school year (6)
Class number, name and grade
Please draw a heating reflux device with tail gas absorption.
2. What is the principle of steam distillation? What is the function of T-tube in equipment? What is an upright long glass tube for? How to judge whether the substance to be steamed has been steamed?
Answer: (1) steam distillation is an operation process in which water is used as the component of mixed liquid, and substances that are basically insoluble in water are distilled out when mixed with water at a temperature lower than 100℃.
⑵ T-tube can eliminate water condensed by steam; Communicate with the atmosphere at any time when abnormal phenomena are found.
(3) The vertical glass tube is a safety tube, which mainly acts as a pressure indicator, and judges the pressure of water vapor by observing the height of water column in the tube; It also has the function of safety valve. When the steam distillation system is blocked, the steam pressure rises sharply, and water can rush out from the upper mouth of the safety pipe, which reduces the system pressure and protects the glass instrument from being broken.
When the distillate has no obvious oil beads and is clear and transparent, it can be judged that the substance to be steamed has been steamed.
3. What is the principle of fractionation? Which organic experiment used fractionator this semester? Please write down the principle of this experiment.
Answer: (1) Fractionator is used to separate components with similar boiling points in the mixture.
⑵ Fractionator is used for preparing cyclohexene.
⑶ Cyclohexene was prepared by dehydration with cyclohexanol as reactant and concentrated sulfuric acid as catalyst.
Please write down the experimental principle of synthesizing 2- methyl -2- hexanol from n-butanol this semester. When preparing 2- methyl -2- hexanol, why do the medicines and instruments used in each step need to be absolutely dried before hydrolyzing Grignard reagent and acetone adduct? What measures have you taken to this end? How to isolate water vapor in reaction operation? Why can't 2- methyl -2- hexanol be dried with anhydrous calcium chloride?
Answer: (1) Experimental principle: n-butanol first reacts with hydrogen bromide to generate n-bromobutane, and alkyl halide reacts with metallic magnesium in anhydrous ether to generate magnesium halide (Grignard reagent). The nucleophilic addition reaction between Grignard reagent and carbonyl compound takes place, and the addition product is decomposed with water to obtain alcohol compounds.
(2) The British reagent butyl magnesium bromide can react with water, carbon dioxide and oxygen.
(3) Isolating moisture and expelling gas from the reaction bottle.
(4) Install a calcium chloride drying tube at the upper openings of the condensing tube and the dropping funnel.
(5) Because calcium chloride can form a complex with alcohol
20 10-20 1 1 organic chemistry examination for applied chemistry in the first semester of the school year (7)
Class number, name and grade
Please draw a device for preparing n-bromobutane. (Same as 6)
2. What is the boiling point? What operation is used to determine the boiling point? Briefly describe the principle and function of this operation.
Answer: (1) At an atmospheric pressure, the gas-liquid equilibrium point of a substance is the boiling point of the substance.
(2) determining the boiling point by distillation; The melting point range of pure liquid compounds during distillation is very small (0.5 ~ 1℃), so the boiling point can be determined by distillation. The operation is not simple, and the boiling point of organic matter can be accurately measured.
What is the principle of steam distillation? What is the function of T-tube in equipment? What is an upright long glass tube for? How to judge whether the substance to be steamed has been steamed?
Answer: (1) steam distillation is an operation process in which water is used as the component of mixed liquid, and substances that are basically insoluble in water are distilled out when mixed with water at a temperature lower than 100℃.
⑵ T-tube can eliminate water condensed by steam; Communicate with the atmosphere at any time when abnormal phenomena are found.
(3) The vertical glass tube is a safety tube, which mainly acts as a pressure indicator, and judges the pressure of water vapor by observing the height of water column in the tube; It also has the function of safety valve. When the steam distillation system is blocked, the steam pressure rises sharply, and water can rush out from the upper mouth of the safety pipe, which reduces the system pressure and protects the glass instrument from being broken.
(4) When the distillate has no obvious oil drops and is clear and transparent, it can be judged that the substance to be steamed is cooked.
4. The esterification reaction is reversible. In the preparation experiment of ethyl acetate, butyl ester and isoamyl ester, the measures taken to make the reaction proceed in the direction of esterification are described.
Answer: Ethyl acetate: excessive ethanol is added to remove water and products at the same time of reaction; Butyl acetate: excessive acid, dehydration during reaction; Isoamyl acetate: excessive glacial acetic acid
20 10-20 1 1 organic chemistry examination for applied chemistry in the first semester of the school year (8)
Class number, name and grade
Please draw all the devices used in recrystallization and point out the names of the devices.
Hot water funnel
2. What is the melting process? What is the difference between the melting points of pure substances and impure substances? What will happen to the melting point of the mixture after two substances with the same melting point are mixed in equal amounts? When determining the melting point, what are the phenomena of judging initial melting and judging total melting?
Answer: (1) The temperature range of pure compounds from initial melting (initial melting) to complete melting (total melting) is called melting range.
⑵ Pure substances have a fixed melting point, while impure substances have a wide melting point range. The melting point will drop after mixing.
(3) Initial melting occurs when the samples fall (collapse, producing liquid phase), and complete melting occurs when all samples become clear liquid.
Where should the thermometer for measuring the boiling point of distillate be placed during distillation operation? At the end of the experiment, who will stop heating and water supply first? Where is the mercury ball of the thermometer when preparing ethyl acetate?
Answer: (1) is placed in the center of the distillation head, and the upper limit of the mercury ball and the lower limit of the branch pipe of the distillation bottle are on the same horizontal line.
(2) Stop heating first, and then stop adding water.
(3) Below the liquid level of reactants.
Please write down the experimental principle of synthesizing 2- methyl -2- hexanol from n-butanol this semester. When preparing 2- methyl -2- hexanol, why do the medicines and instruments used in each step need to be absolutely dried before hydrolyzing Grignard reagent and acetone adduct? What measures have you taken to this end? How to isolate water vapor in reaction operation? Why can't 2- methyl -2- hexanol be dried with anhydrous calcium chloride?
Answer: (1) Experimental principle: n-butanol first reacts with hydrogen bromide to generate n-bromobutane, and alkyl halide reacts with metallic magnesium in anhydrous ether to generate magnesium halide (Grignard reagent). The nucleophilic addition reaction between Grignard reagent and carbonyl compound takes place, and the addition product is decomposed with water to obtain alcohol compounds.
(2) The British reagent butyl magnesium bromide can react with water, carbon dioxide and oxygen.
(3) Isolating moisture and expelling gas from the reaction bottle.
(4) Install a calcium chloride drying tube at the upper openings of the condensing tube and the dropping funnel.