What is the primary process of a photochemical reaction

The primary process of photochemistry is that the molecule absorbs photons to excite the electron, and the molecule is promoted from the ground state to the excited state.

The electron state, vibrational and rotational states in a molecule are all quantized, i.e., the energy changes between adjacent states are discontinuous. Therefore, the amount of photon energy required when the initial state of the molecule is different from the termination state at the time of excitation.

It is also different, and the energy values of the two are required to match as much as possible. Since the energy of the photon hv hc (where h is Planck's constant.

v is the frequency of light; is the wavelength of light; c is the speed of light), so the energy matching is reflected in the matching of the wavelength of light.

Primary processes of photochemistry.

A certain molecule or atom can only absorb photons of a certain energy, and the excited molecule after absorbing light energy is in an unstable state, and can become a stable state due to the loss of energy in many ways.

The primary process mainly refers to the formation of excited state substances after chemical substances absorb light quanta, and its basic steps are:

A (a certain chemical substance) + HV (light quantum of a certain wavelength) A* (excited state substance).

There are four fates of matter in the excited state:

1) A* A+HV (radiative transition, fluorescence occurs, energy loss, return to ground state, photophysics).

2) a*+m (other molecules) a+m (no radiative transition, collision consumes activation energy, returns to ground state, photophysics).

3） a*→b1+b2+……Photodecomposition, dissociation occurs, photochemistry).

4） a*+c→d1+d2+……Photosynthesis, direct reaction with other substances, photochemistry).

For example, atmospheric glow (i.e., the phenomenon of the atmosphere emitting light at night) is a radiative transition caused by a fraction of the excited oh· (free radicals).

o3 + h ® oh*· o2

oh*·®oh· +hn

Photolysis of oxygen atom O2 + Hv O* O·+O·

Nitrosyl chloride: NOCL + HV NOCL*

nocl*+ nocl®2no+cl

Wrong. It is clear in the textbook that the dark reaction can be carried out in both light and dark states, but the process does not require light.

In the dark reaction stage, the green leaves inhale carbon dioxide from the outside world through the stomata and cannot be directly reduced by reduced hydrogen. It must first bind to C5 (a five-carbon compound, ribulose diphosphate) in the plant, a process called carbon dioxide fixation. After one carbon dioxide molecule is immobilized by a C5 molecule, two C3 (a three-carbon compound, 12-glyceraldehyde-3-phosphate) molecules are formed very quickly.

Catalyzed by the enzymes, C3 receives the energy released by ATP and is reduced by reduced hydrogen. Subsequently, some C3 that receives energy and is reduced by reduced hydrogen undergoes a series of changes to form sugars; Other C3 that receives energy and is reduced by reduced hydrogen undergoes a series of chemical changes to form C5, so that the chemical reaction in the dark reaction stage continues. It is referred to as carbon-fixation reaction.

In this reaction, chloroplasts use two high-energy compounds, ATP and Nadph, produced by the light reaction, as energy and reduction power, respectively, to fix CO2 and convert it into glucose, which is called a dark reaction because no light is required for this process. The carbon fixation reaction (carbon reaction) begins in the chloroplast matrix and ends in the cytoplasmic matrix.

Photoreaction stage The chemical reaction in the first stage of photosynthesis must have light energy to proceed, and this stage is called the photoreaction stage. The chemical reaction in the photoreaction stage is carried out on a capsule-like structure film within the chloroplast.

In the photoreaction stage, the pigments in the chloroplast absorb light energy, and these light energy are used in two ways: on the one hand, it is to decompose water molecules into oxygen and hydrogen [h], which is directly released in the form of molecules, and hydrogen [h] is transferred to the matrix in chloroplasts as a lively reducing agent to participate in the chemical reaction in the second stage; On the other hand, under the catalytic action of the relevant enzymes, the shield promotes the chemical reaction between ADP and PI to form ATP. Here, the light energy is converted into chemical energy and stored in ATP.

These ATPs will be involved in the chemical reactions in the second stage.

Dark Reaction Phase The chemical reaction in the second stage of photosynthesis can be carried out without light energy, and this stage is called the dark reaction stage Sakura stage. The chemical reactions in the dark reaction phase are carried out in the matrix within the chloroplast.

In the dark reaction stage, the carbon dioxide absorbed by the green leaves from the outside world cannot be directly reduced by hydrogen [h]. It must first combine with a five-carbon compound in the plant (abbreviated as a five-carbon compound, denoted by C5), a process called carbon dioxide fixation. After a carbon dioxide molecule is fixed by a five-carbon compound, two compounds containing three carbon atoms (abbreviated as three-carbon compounds, denoted by C3) are quickly formed.

Catalyzed by the enzymes involved, the three-carbon compounds receive the energy released by ATP and are reduced by hydrogen [H]. Among them, some three-carbon compounds undergo a series of changes to form sugars; Other three-carbon compounds undergo complex changes to form five-carbon compounds, so that the chemical reaction in the dark reaction stage continues in a reciprocal cycle.

The photoreaction is also known as the photosystem electron transfer reaction (photosythenicelectron-transfer).

reaction)。During the reaction, the light energy from the sun causes the chlorophyll of green organisms to produce high-energy electrons, which convert light energy into electrical energy. The electrons are then transported through the electron transport chain in the chloroplast thylakoid membrane.

and transfer H+ protons from the chloroplast matrix to the thylakoid lumen to establish an electrochemical proton gradient for ATP synthesis. The last step in the light reaction is when the energetic electrons are accepted by NadP+, allowing them to be reduced to Nadph. The site of the light reaction is thylakoids.

In a nutshell, light reaction is the process by which photosynthetic pigment molecules such as chlorophyll absorb light energy and convert light energy into chemical energy to form ATP and NADPH. The photoreaction consists of three main steps: light energy absorption, electron transport, and photosynthetic phosphorylation.

Photosynthesis can be divided into 3 major steps.

1. Primary reaction, including light absorption, transmission and conversion.

2. Electron transport and photosynthetic phosphorylation to form active chemical energy (ATP and NADPH) 3. Carbon assimilation to convert active chemical energy into stable chemical energy photochemical reactions.

Electron transport and photosynthetic phosphorylation.

The transfer of electrons through a series of electron transporters causes the cleavage of water to release oxygen and the reduction of NaDP+ to Nadph, and the formation of ATP through photosynthetic phosphorylation

A photochemical reaction is a chemical reaction triggered by an atom, molecule, free radical or ion absorbing a photon.

Photochemical reactions in the environment are mainly irradiated by sunlight, and pollutants absorb photons and make the molecules of the substance in a certain electron excited state, causing chemical reactions with other substances. For example, the initial reaction of photochemical smog formation is a photochemical reaction in which nitrogen dioxide (NO2) absorbs ultraviolet rays (wavelength 2900 4300A) and decomposes into nitric oxide (NO) and atomic oxygen (O, triplet) under sunlight, which starts the chain reaction, resulting in a series of reactions with ozone and other organic hydrocarbon compounds and finally forming toxic products of photochemical smog, such as peroxyacetyl nitrate (PAN).

photochemical reactions and actinic reactions; It is an application concept.

Title: Photochemical Reaction English Name: Photochemical Reaction Photochemical reaction or actinization.

The chemical reaction of a substance under the exposure of visible light or ultraviolet light is a reaction triggered by the absorption of photons by the molecules of a substance. It can cause processes such as compounding, decomposition, ionization, oxidation, reduction, etc. There are two main types: photosynthesis and photolysis.

Chinese name: photochemical reaction English name: photochemical reaction Definition:

A chemical reaction that occurs when a substance absorbs light energy when exposed to visible or ultraviolet light. It can cause processes such as compounding, decomposition, ionization, oxidation, reduction, etc. There are two main types: photosynthesis and photolysis.

Applied Disciplines: Resource Science and Technology (First-level Discipline); Climate Resources Science (Secondary Discipline).